13 Closer Fantasy Baseball Breakout Candidates: Relief Pitcher Targets For Saves (Week 4)

April 21, 2026

Nick looks at 13 potential fantasy baseball breakouts, sleepers for closers and saves for Week 4 of 2026. His top relief pitcher waiver wire and trade targets for saves.

Boy, if y'all thought that closer chaos and bullpen madness had reached an early climax, this past week proved that there is always more crazy in the tank. Allow this column to try to help you keep one foot on the ground as the whirlwind throws us around. Let's make the call to the 'pen for this week's relief risers and potential breakouts.

This article aims to identify surging arms and closer candidates for targeting, whether it's a short-term play or for those stashing away some RP depth. We're now sifting through plenty of injury fallout and once-reliable arms going through turbulent times, but it's still early, and so we'll still orbit data such as strikeouts, walks, and pitch usage/velocity, with most intel gathered on April 20. Perhaps you're in deep waters, and most of these are trade targets rather than waiver adds, but it is all worth discussing.

It's easy to forget that we're just getting into late April and the weather is (sort of) warming up. And injury stashes that you may have been relying on for future production are no sure thing to come to fruition! You've got to join the resident Mariano for a closer chat about MLB bullpens going into Week 4 of the 2026 fantasy baseball season.

Tanner Scott & Alex Vesia, Los Angeles Dodgers

Edwin Diaz will miss three months to get loose bodies in his elbow removed, despite the poor early form and diminished velocity being waved off as normal post-knee-injury April. We're to believe this is a new issue, so hopefully the velo comes back with a rested knee in three months then?

Yesterday was the first time Edwin Díaz felt discomfort in his elbow, Dave Roberts said — but Dodgers obv believe that’s what’s been causing issues with his velocity

MRI revealed the loose bodies, but no structural damage to ligament

Roberts had loose bodies as a player and…

— Jack Harris (@ByJackHarris) April 20, 2026

Dave Roberts says there are a “handful” of relievers that he’s comfortable using in the ninth, yet he’s surely shown his hand already. Vesia has the only two other Dodger saves so far, and is an obvious riser into an all-formats add. Scott has four holds, a wealth of closing experience, and a perfect 8:0 K:BB in 8 ⅔ IP.

We spoke highly of them last week, so I won’t drone on again. If I had it my way, we’d just see Scott slide into the role and not be punished for his health-maligned 2025 campaign.

Blake Treinen is surely in the mix based on history and 2026 usage (four holds), but the 4.17 xERA ballooned to 7.73 after three runs and no outs at Coors. Perhaps you’re willing to chalk that up to his getting beamed during pregame warmups on Saturday? I’d rather chase Jack Dreyer (9 ⅓ IP, 11:4 K:BB, 1 ER, 2.51 xERA).

If you think a few more crummy Roki Sasaki starts lead to a bullpen pivot, then the path is now widened! River Ryan’s hamstring injury seemingly takes away from that plan at the moment, however.

Caleb Thielbar & Ben Brown & Riley Martin, Chicago Cubs

The Cubs only got one save out of Daniel Palencia across three weeks following his scorching World Baseball Classic before an oblique injury knocked him down. Obliques are notorious for sapping power for hitters, but pitchers need to be able to twist and transfer all of that power up the chain to their arms. It could be a while.

This is a particular issue with Phil Maton, Hunter Harvey, and Porter Hodge also hurt. So, what are we digging deep for in Wrigleyville?

Thielbar is the veteran with the most MLB experience of the remaining arms, and he got the first save. Brown has shown flashes, but his sabermetrics greatly outpaced his results over 106 ⅓ IP as a swingman last year. His 2025 verdict comes down to your buying the 25.6% strikeout rate with a 3.52 SIERA and 3.56 xFIP, or the 5.92 ERA/1.44 WHIP/1.52 HR/9.

Another issue for us is that Brown’s stamina has gone at least two innings in all seven of his appearances. A beleaguered bullpen won’t shy away from length. He’s also one of the few right-handed pitchers they’ve got left!

And then Martin has gotten off to a hot start, blanking opponents with a 7:0 K:BB over 6 ⅓ IP for a 0.92 FIP and 1.84 SIERA. He is 28, so take his 2025 Triple-A numbers with a grain of salt, but a 30.7% K rate with a 2.69 ERA/1.19 WHIP/3.54 FIP combo is far better than the 32.7% K/4.48 ERA/1.61 WHIP/4.28 FIP in ‘25.

Walks and control have been his undoing, but he bumped his first-strike rate up four percentage points alongside a five-point bump on the groundball rate. Well, zero walks over 22 batters faced is extremely encouraging! This could be his chance to quickly blossom in a time of need.

Enyel De Los Santos, Houston Astros

De Los Santos is still about two full ticks down from his 2025 velocity, but he’s leaning on the fastball less and throwing his changeup at a career-high 30.6% clip. Percentages can shift early, but we’re talking double his ‘25 offspeed rate. All 10 batted balls off of it have resulted in outs, which does have some luck, but a .111 xBA and .187 xSLG sure look deserving.

We still don’t love that his lowly 3.4% walk rate comes with a dip in first-strike rate versus his past two years, but hitters are really struggling to square him up, even in an advantageous count. I don’t think the magic lasts long, but if he stays hot for much of the next month (until Josh Hader’s 60-day IL stint is up), then we’re happy.

Brad Keller, Philadelphia Phillies

Let the converted starter trend continue! Keller is in line to receive the “bulk” of saves for Philadelphia with Jhoan Duran (oblique) on the shelf. The team is calling that mild, but I’ve never met a minor oblique issue. Jose Alvarado can work into the mix if a left-hander is needed in the ninth, but we’ll take Rob Thomson at his word (for now!).

Brad Keller will get the bulk of closing opportunities while Duran is out. https://t.co/BXJzLzT9Ej

— Todd Zolecki (@ToddZolecki) April 18, 2026

Don’t be distracted by the 4.15 ERA/1.27 WHIP, as Keller looks very similar to last season’s breakout (2.07 ERA/0.96 WHIP/27.2% K rate). In fact, his 3.04 xFIP and 2.83 SIERA are lower than last year in the early going, and the 62.5% groundball rate is threatening to dust the 56.1% figure he delivered in ‘25.

Louis Varland, Toronto Blue Jays

The Blue Jays are sticking with Jeff Hoffman for now, likely inspired by the .571 BABIP and 1.74 HR/9 being unlikely to hold. Or sunk cost fallacy, eh? While the BABIP is certain to fall (~.250 since becoming a reliever outside of Coors), he did have a 1.99 HR/9 last year.

They shouldn’t stomach much more with Varland following in Hoffman’s SP-into-RP footsteps. He pitched to a 2.97 ERA/1.20 WHIP last year with a near-identical 3.14 FIP/3.10 xFIP/3.13 SIERA over 72 ⅔ IP, which fueled Toronto’s deadline acquisition of the reliever.

This season has seen him cruise to a 19:3 K:BB over 12 1/3 IP without allowing an earned run, scattering eight hits (zero barrels). His 98-mph fastball has been outstanding, yielding just one hit (.095 xBA/.108 xSLG prior to Monday’s game). Talent may soon meet opportunity here, though Hoffman had a nice night on Monday.

Matt Strahm & Daniel Lynch IV, Kansas City Royals

Word was that Carlos Estevez was hoping to begin a rehab assignment by Sunday, but it’s Monday night, and I haven’t seen anything more. What I did witness on Monday was another poor effort from Lucas Erceg, who allowed the tying run via three walks and a hit with no strikeouts.

Strahm struck out the side in the eighth ahead of Erceg, and then Lynch was perfect for his four batters faced (two strikeouts), though he was charged with the placed runner in the 11th since he started the frame. (Dumb.) Erceg is better than Estevez, but the bar was set in the Mariana Trench.

This piece would’ve read differently had Strahm not looked so good, but perhaps we’re back. He’d allowed three runs with a 3:3 K:BB over his last four innings, though 15 career saves could give Matt Quatraro faith to pivot from Erceg.

Lynch was, you guessed it, a failed starter in 2021-23, but he’s off to a 12:3 K:BB with one earned run allowed in nine innings. Caveat emptor, as the WHIP is riding a .111 BABIP, but he’s leaning far more on a sinker (19% in ‘25 to 31%) with an 80 mph average exit velo, 35.7% whiff rate, and .220 xSLG. He also has five strikeouts on the slider against just two batted balls. Not hits, batted balls!

*The next three names are certainly more on the “periphery,” but bring intrigue nevertheless.

Antonio Senzatela, Colorado Rockies

Let’s stick with the starters in the ‘pen! Senzatela was one of the worst pitchers in 2025, but now his Savant page’s icy blue row is followed by nothing but red. His fastball is up from 95 mph to 97.2 as a reliever, though he’s throwing it less (57% to 38%) in favor of more cutters and sinkers.

This has helped him earn more whiffs, gaining an 11% swinging-strike rate (7.6% last year), and more grounders (56.3% from 45.6%). Mitigating contact, especially loud and upward contact, is crucial. The resulting 17:3 K:BB with one run allowed over 14 ⅓ IP is fantastic.

He’s comfortable throwing that cutter to both sides of the plate, and he remains a viable five-pitch threat to both lefties and righties. That’s what coming up as a starter can do! No Coors pitcher is certain, and I’m not saying he’ll become their closer. Much like Brown in Chicago, his innings and endurance are valuable.

Mason Montgomery, Pittsburgh Pirates

We’ve said that Montgomery’s raw talent is some of the best stuff cooking across MLB bullpens, but inconsistent command can bog him down. Much of the preseason hype evaporated when he walked three and allowed two runs in his first game, giving up another pair of runs in his third appearance.

Yours truly was also locked onto watching Gregory Soto outpitch Dennis Santana, which I still believe. But we can’t lose sight of Montgomery, who has a 13:1 K:BB with one run allowed on seven hits in 6 ⅓ IP since that third game. The .538 BABIP in that stretch is still frightful, and it can point to punished mistakes, but even that will calm down. Pittsburgh’s bullpen is fun!

Gavin Collyer, Texas Rangers

Collyer has triple-digit heat and a potent sweeper to headline a four-pitch arsenal (cutter, sinker) that could see him swiftly ascend a shaky leverage ladder. He showed off the good with three strikeouts over two innings in his MLB debut, but also the bad in two walks.

Gavin Collyer strikes out the first batter he faces in the big leagues!@RangersSNtv | #MLB pic.twitter.com/u2yAiSl9dR

— Victory+ (@victoryplustv) April 16, 2026

The fireballer has always possessed high-whiff stuff, but is just breaking in at nearly 25 years old due to too many mistakes in and out of the zone. His last three minor-league BABIPs, from 2023 through ‘25, were .320, .390, and .320, with walk rates of 11.7%, 13.5%, and 16%. That’s a lot of traffic to deal with, resulting in WHIPs in the 1.50-1.60 range.

But he showed growth in six Triple-A games, posting an 11:2 K:BB with two runs allowed on five hits. And frankly, Texas can’t afford to be choosy at this time. Jakob Junis and Cole Winn are still the favorites, but Robert Garcia is undergoing a shoulder MRI, and there isn’t much keeping someone like Collyer away from high leverage.

Quick Hits:

-Dylan Lee snagged three holds over the last week with four Ks in 3 ⅓ IP.
-Adrian Morejon looks “back” with 4 IP, 0 ER, 5 K, 2 HLDs since early-April trouble.
-Congrats to Graham Ashcraft on his first career save (both Emilio Pagan and Tony Santillan were resting).
-Another two wins for Aaron Ashby since last week’s article. Sheesh!
-Drew Pomeranz and Sam Bachman remain sturdy stashes, but maybe Jordan Romano just hates Yankee Stadium? He struck out three in a shutout frame vs. SD on April 17.
-Keaton Winn, Erik Miller, and Caleb Kilian all continue to pitch well. Throw those darts!
-Will Connor Prielipp get a chance for Minny, or just be a procedural taxi squad guy?

Connor Prielipp will join the #MNTwins in New York on Tuesday, but for now is designated as being on the team’s taxi squad.

Prielipp has a 2.30 ERA with 22 strikeouts in 15 2/3 IP at Triple A.

— DanHayesMLB (@DanHayesMLB) April 20, 2026

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