Fantasy Baseball Trade Targets - Buy/Sell for Week 4 (2025)

Fantasy baseball trade candidates to buy/sell for Week 4 (2025). Joey's fantasy baseball undervalued players to target in trades, and overvalued to trade away.

We are at a point in the season where some fantasy managers might panic about certain players. Even though we are only three weeks into the fantasy season, plenty of early-round picks have not lived up to their standards. Some of those stars include Francisco Lindor, Juan Soto, and Gunnar Henderson. However, those players won't be easy to trade for, which is why they won't appear on this list. 

If you do own Lindor, Soto, or Henderson, you should continue to hold them because it's only a matter of time until they start producing elite numbers. Since they won't be featured in this week's edition, we will go through five different players fantasy managers should be looking to buy/sell ahead of Week 4 (April 21 to April 27). 

So, which players should we buy and sell for Week 4 of the 2025 fantasy baseball season? Let's dive in and find out which big-name players make the list. 

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Undervalued Fantasy Baseball Players to Trade For

Julio Rodriguez, OF, Seattle Mariners 

It's not a major surprise to see Seattle Mariners outfielder Julio Rodriguez struggle offensively out of the gate. This has become the norm for the two-time All-Star. In 2023, Rodriguez had a .204 batting average with seven home runs and 21 RBI across his first 44 games. Then, last season, he had just a .206 AVG with one extra-base hit in his first 18 contests. 

Julio Rodríguez drives in two and ties this game up in the 9th inning! pic.twitter.com/LMQmrD8k6r

— MLB (@MLB) April 9, 2025

So, are we really shocked that Rodriguez is batting only .187 in his first 19 games? That slow start, though, makes him a great buy heading into Week 4. It's a good sign that he already has six extra-base hits (one double, two triples, and three home runs) with five stolen bases this early in the year, and the Mariners outfielder always seems to pick it up as the season goes on. 

Rodriguez hit .302 at the plate with 25 home runs, 82 RBI, and 29 stolen bases over the final 111 games of the 2023 season and then batted .281 with 20 home runs and 20 stolen bases from April 20 onward last year. As a result, his bat will heat up in the coming weeks. 

Even though Rodriguez only has an expected .237 batting average, his average exit velocity (93.6 mph), hard-hit rate (55.3 percent), and bat speed (75.3 mph) are all fantastic signs for him moving forward. That means fantasy managers should be trying to make a move for him right now. This player has the potential to hit at least 30 home runs and steal over 30 bases in 2025. 

Ian Happ, OF, Chicago Cubs

Very few fantasy managers should be panicking about Chicago Cubs outfielder Ian Happ's production in the early going. While he has gotten off to a slow start, we know what to expect from the three-time Gold Glove winner. He'll play over 150 games while carrying a .245 batting average with 20-plus home runs, 80-plus RBI, 85-plus runs scored, and double-digit stolen bases. 

Although he is batting just .233 with only one home run and eight RBI in his first 21 games this season, he's someone fantasy managers should be buying low at this point in the year. Happ had a similar cold streak to start the 2024 campaign after hitting .219 with one home run and 13 RBI across his first 39 games.

Nevertheless, that cold streak didn't last for much longer, as the former All-Star batted .251 with 24 home runs and 73 RBI over the final four months of the season. So, make a move for him now before the weather warms up. His .265 xBA is 32 points higher than his actual batting average (.233), and his high walk rate (11.7 percent) will continue to help him get on base. 

Christian Walker, 1B, Houston Astros  

It has not been a strong start to the season for Houston Astros first baseman Christian Walker. After leaving the Arizona Diamondbacks this past offseason, Walker's new home hasn't been treating him well through the first three weeks. The slugger is batting just .154 with one home run and two RBI in 18 games. 

Christian Walker stays golden.

Congrats on your third consecutive @RawlingsSports Gold Glove, Christian! pic.twitter.com/Wx0Vp7ssMF

— Houston Astros (@astros) April 12, 2025

Nothing about Walker's start to the season has been encouraging. He has a 30.7 percent strikeout rate, a 21.4 percent launch angle sweet-spot rate, and a 19.3 percent squared-up rate to begin the year. However, we should bet on the first baseman's talent and stay patient with him through this slump. 

His elite bat speed (74.4 mph) should help him produce throughout the year, and Walker will likely finish with his usual power numbers by the end of the season. Given that he plays all his home games at Daikin Park with that short porch in left field, the veteran should hit over 25 home runs for the fourth consecutive year. Therefore, fantasy managers should be buying him amid this cold offensive stretch. 

Overvalued Fantasy Baseball Players to Trade Away

Marcus Semien, 2B, Texas Rangers

Age might finally be catching up to Texas Rangers second baseman Marcus Semien. Semien had a down year in 2024, and concerns surrounded him entering the fantasy season. His 23 home runs, 27 doubles, 74 RBI, eight stolen bases, and 154 hits last year were all his fewest in a full season since 2018. 

Unfortunately, Semien's struggles have continued early in 2025. He is batting just .134 with one home run, one double, and six RBI across 17 games to begin the season. While he won't hit this poorly all year, we might have seen the last of the veteran in his prime. His barrel rate (5.8 percent), hard-hit rate (30.8 percent), and whiff rate (24.1 percent) are all concerning signs for him heading into Week 4. 

That makes Semien a sell in most fantasy formats right now. Fantasy managers should be worried about his early-season numbers, and now might be the best time to get rid of him. Given the way he has looked offensively, it's hard to want to keep him on your fantasy team.

Don't forget, the three-time All-Star hit just .219 with seven home runs in the final two months of the 2024 season. So, this start might be more than just a cold streak for Semien. 

Mitchell Parker, SP, Washington Nationals

Washington Nationals starting pitcher Mitchell Parker is off to a great start on the mound. After showing some promising things in his rookie campaign in 2024, Parker has taken his pitching to the next level to begin the 2025 season. He has allowed just five earned runs across 24 1/3 innings pitched (1.85 ERA) to go with 16 strikeouts and a 1.11 WHIP. 

It's definitely encouraging to see the southpaw deliver four straight quality starts to begin the year, which included throwing six 1/3 shutout innings against the Philadelphia Phillies back on March 29. However, if you are one of the few fantasy managers who own Parker, you should try to sell him as soon as possible.

Mitchell Parker, Dirty 86mph Slider. 😨

5th K pic.twitter.com/AoA1UAvpgF

— Rob Friedman (@PitchingNinja) April 16, 2025

Although the results have been there for the left-hander to start the season, his low strikeout rate (15.8 percent) and high hard-hit rate (43.2 percent) suggest that Parker might not be that hidden gem off the waiver wire after all. With some negative regression possibly coming, fantasy managers should be looking to sell him heading into Week 4. 

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