3 Impressive Fantasy Baseball Breakout Pitchers - Roki Sasaki, Trevor McDonald, Griffin Jax

May 20, 2026

Andy looks at three starting pitcher fantasy baseball breakouts, sleepers off to hot starts in 2026. Are Roki Sasaki, Trevor McDonald, and Griffin Jax for real?

Finding breakout starting pitchers on the waiver wire can provide your fantasy team with a massive spark. Through the early part of the 2026 season, many starting pitchers have surpassed preseason expectations and have put themselves in "must-start" status, such as Cam Schlittler, Jacob Misiorowski, and Chase Burns.

Last week, we took a look at three starting pitchers who were on a breakout trajectory, such as J.T. Ginn, Peter Lambert, and Ben Brown, with Brown and Ginn both turning in the best starts of their campaign in their last appearances. As a result, it's time to look at another three emerging pitchers and determine if managers should pick them up off the waiver wire.

Should managers look to add these three starting pitchers before they continue their breakout season? Let's dive in! Note - All advanced statistics referenced are updated as of Tuesday, May 19.

Roki Sasaki, Los Angeles Dodgers

35% Rostered

The 24-year-old sensation was considered a must-draft "rookie" last season after he made the move to the major leagues following a dominant stretch overseas. However, the right-hander faced major growing pains when transitioning to the major leagues and was likely sent to the waiver wire in most leagues. He did not draw much hype heading into the 2026 draft season.

In 2025, Sasaki logged just 36 1/3 innings ot the tune of a 4.46 ERA and a 1.43 WHIP. He struck out just 28 hitters and posted a high 13.7% walk rate. He would miss most of the campaign due to a right shoulder injury. He would eventually return to action later in the second half but would transition to the bullpen, where he would begin to showcase the promised upside.

Heading into the 2026 season, the Dodgers did not guarantee Sasaki a spot in the rotation, but given that Blake Snell began the season on the shelf, the 24-year-old slid into one of the final spots. Over the first 28 2/3 innings of work this season (six outings), Sasaki did not show much progress, and managers who were hoping to secure a post-hype breakout likely cut ties.

However, over his last two outings, Sasaki has begun to rekindle his previous form and could be making the necessary adjustments at the MLB level.

In his last two games (12 innings), Sasaki has allowed four runs while posting a strong 13:1 K:BB. Much of this production came in his outing on May 17 when he tossed seven innings of one-run ball against the Angels with a season-high eight punchouts. Has Sasaki made the necessary adjustments to begin to turn the corner?

When looking at his pitch mix last year, Sasaki continued to lean on his four-seamers but dropped forkball usage from 33.5% to a much-lower 17.7% this season. In 2025, his forkball was his No. 2 pitch, but it has since dropped to his No. 3 overall pitch this season. Instead, he has turned to a slider as his No. 2 option and added a split-finger to serve as the No. 4.

Compared with April and May, Sasaki has made one notable change that could explain his increased success. While he leaned on his forkball heavily in April, as he did for most of 2025, he has since shifted to a split-finger in May and dropped his forkball usage significantly.

By increasing the use of his split-finger, his four-seamer and slider have begun to perform much better. His split-finger has been nothing short of dominant in May, posting an elite 42.9% whiff rate with a .217 wOBA. While the .304 xwOBA under the hood suggests it may have gotten a bit lucky, it should remain a strong secondary option.

However, by relying more on this pitch, his four-seamer has played much better. In May, this pitch has generated a .392 xwOBA, which is still concerning, but a stark drop from the .503 xwOBA it posted in April. The other pitch to monitor is his slider. In both months, this pitch has ranked as his No. 3 pitch in usage, but it took a dramatic step forward in May.

As shown below, the pitch has not only generated a much higher whiff rate, but also lowered its xwOBA by nearly 300 points, holding a low .116 xwOBA throughout his first three outings in May.

While the overall 5.11 xERA and .262 xBA suggest he should take a further step back after this recent surge, Sasaki has elite secondary pitches that are likely to continue to drive his strikeout totals. While Sasaki will need to improve his four-seamer to enjoy consistent success, he is flashing enough upside to warrant a pickup in all standard leagues and deployed in favorable settings.

If he can continue to lower his walk rate (8.8% BB%, 52nd percentile) and generate high whiffs (29.0% whiff rate), he will hold the upside to entertain must-roster conversion.

Trevor McDonald, San Francisco Giants

20% Rostered

After spotlighting a potential post-hype breakout, let's take a look at a rookie starting pitcher. Trevor McDonald actually made his MLB debut in 2024, but given that he only logged three innings that season and just 15 in 2025, he still carries his rookie stats and entered the 2026 season as the team's No. 160-ranked prospect, per MLB.com.

However, after two brief MLB stints over the past two seasons, it appears McDonald is finally settling into a full-time role in the Bay Area. McDonald made his season debut on May 4 in a spot-start against the San Diego Padres. In this outing, the right-hander logged seven innings of one-run ball with two hits, no walks, and eight punchouts.

He then returned to the majors on May 11 to face the Dodgers in Los Angeles, but lived up to the task. Against the reigning two-time world champions, McDonald tossed 5 1/3 innings of three-run ball with a modest 4:2 K:BB. However, in his third outing on May 16, McDonald quickly returned to form, tossing 6 2/3 innings with one earned run and five strikeouts against the Athletics.

Overall, the 25-year-old has posted a strong 2.37 ERA with a 1.00 WHIP over his first 19 innings this season. While the sample size is small, McDonald is flashing high-end upside worth a closer look.

McDonald has relied on three pitches in his repertoire, but has leaned heavily on his top two. His No. 1 pitch is a sinker, which he has thrown 57.4% of the time, averaging 94.2 MPH. This pitch has been very effective, posting a .285 xwOBA with a solid 15.8% whiff rate. His No. 2 pitch, his slider, has been the primary source for strikeouts.

He has deployed this pitch 29.4% of the time, and it has drawn swings and misses at an elite 42.1% clip while generating a .153 wOBA. His No. 3 pitch is his changeup, which has just been mixed in 12.5% of the time, but has been effective in the strikeout department as well.

Like his slider, this has generated a high 42.9% whiff rate but holds a much higher .678 xwOBA, suggesting it allows loud contact.

Like Sasaki, his cumulative 3.79 xERA suggests he is outperforming his current metrics, but he should still be a very serviceable fantasy pitcher. His sinker allows weak contact, and his slider and changeup are effective in drawing whiffs.

While his No. 3 option will need to limit damage, the foundation is there for McDonald to hold high-end SP4/SP5 upside in deeper 12+ team leagues.

Griffin Jax, Tampa Bay Rays

30% Rostered

The final pitcher we will spotlight has recently transitioned to a starting role earlier in May. Griffin Jax was viewed as one of the most dominant setup arms in baseball and carried elite upside in saves+holds leagues. In 2024, Jax enjoyed a career year with the Twins, logging 71 innings to the tune of a 2.03 ERA and a 0.87 WHIP.

During this campaign, Jax racked up an eye-catching 95 punchouts while adding 24 holds and 10 saves. In 2025, he took a step back, posting a 4.23 ERA but still added 28 holds while generating 35.0% K%.

In 2026, Jax was in discussions to potentially earn save opportunities in a wide-open Rays bullpen, but got off to a slow start, which pushed him to also have an elevated role. Over his first four appearances (two innings), he posted a 22.50 ERA and a 3.50 WHIP and took two losses with two blown saves. While this start sent him to the waiver wire in nearly all leagues, he has begun to slowly turn the corner.

From April 5 through April 18 (5 2/3 innings), he held a 1.59 ERA with a 9.5 K/9, which was far more in line with his career marks. However, since his outing on April 21, the team has begun to stretch his workload and has recently moved him to a starting role.

On April 26, he made his first start of the season, logging 2 1/3 innings in an "opener" where he did not allow a run while striking out two hitters. Since then, his workload has gradually continued to increase, with his season-high of five innings of work coming in his most recent game on May 13.

In this start, he tossed five-hit shutout frames against the Blue Jays and allowed just four hits. However, he struck out just one hitter while walking four. While the lower strikeout totals are concerning, Jax is beginning to look like his pre-2025 self, which is a great sign for his rest-of-season outlook.

Given that Jax is finding his footing in a new role, we will only examine his recent pitch mix as the most telling indicator of his long-term upside. In the visual below, we can see that over his last two outings (his longest starts), Jax has leaned less on his four-seamer and instead deployed his sweeper at nearly the same rate.

Overall, this season, his four-seamer has been the cause of much of his struggles. Entering May 19, this pitch generated a high .536 xwOBA and a low 18.8% whiff rate. TI has allowed a hefty .878 xSLG with a .737 SLG on the surface, suggesting that he could even see further struggles with this pitch, given the loud contact is surprising.

However, his sweeper has been the complete opposite. It has generated a significantly lower .238 xwOBA with a dominant 44.2% whiff rate. Even though his K% is on pace to be the lowest of his career, if he continues to lean on this pitch as his "No. 1" option, those K% and whiff% totals should continue to climb back to his career norms.

While this new pitch is at the bottom of the visual, he has been throwing it in May and could become a trusted secondary later in the summer. His curveball has been thrown a low 3.6% of the time in May (6.0% on the year), but has generated a 36.4% whiff rate this season in the small sample.

If Jax can continue to mix this with his already elite sweeper and solid changeup, he could find three high-end whiff options. Managers should not rush to the waiver wire to add Jax, given his minimal track record as a starter. However, his most recent outing suggests he is turning the corner and could eventually hold high-end streaming potential.

Jax extended this breakout trajectory on Tuesday evening as he logged five innings of one-run ball with six strikeouts. His command looked far better in this showing as he walked just one hitter.

His track record of being a dominant strikeout option may not translate to a starting role, but the raw upside is still there. For now, he is a name to stash in standard leagues and could firmly enter the streaming radar after a string of impressive outings.

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