Fantasy Baseball 2021: Best Sleepers to Pick Up for MLB Week 21

Things are heating up heading into the stretch run of the 2021 Major League Baseball regular season. 

This also means business is picking up in the fantasy baseball world. The waiver wire is still the best way to find a cheap upgrade for your roster, especially if injuries or an unexpectedly poor performance from one of your current starters is dragging you down. 

Three weeks removed from the trade deadline, teams that were sellers have now likely settled on the players they want to see perform over the final six weeks to determine where they might fit into the plans for 2022. 

That means fantasy managers can take advantage of a hot streak from a once-hot prospect or a player returning from injuries to make a move up the standings. 

Looking at the list of players available in at least 40 percent of ESPN leagues, here are the best ones to pick up right now. 

A first-round pick by the Texas Rangers in 2012, Lewis Brinson's career has always been more about the potential than the performance. He was a key piece in two separate trades, starting with the Rangers acquisition of Jonathan Lucroy from the Milwaukee Brewers in July 2016. 

Less than two years later, the Brewers flipped Brinson to the Miami Marlins in the Christian Yelich trade. It speaks well to how highly teams view his talent that he could be traded for a former All-Star catcher and an MVP. 

In his first four MLB seasons from 2017-20, Brinson bombed with a .189/.242/.304 slash line in 821 appearances over 252 games. He remained on that track in the first half of 2021 with a .585 OPS in 28 games. 

Some of Brinson's early struggles this season can be attributed to the yo-yoing the Marlins were doing with him. He has been optioned and recalled from the minors eight different times. 

Since his most recent recall from Triple-A, Brinson has looked like a new player. The 27-year-old has a .309/.371/.593 slash line in the past 25 games. 

Per Kenny Kelly of Beyond the Box Score, one reason to be optimistic about this hot streak for Brinson is he's decreased his ground-ball rate from a career mark of 51.6 percent to 42.1 since July 19 when he returned to Miami. 

Brinson does still have contact issues with 21 strikeouts in 81 at-bats during this 25-game stretch. His average is certainly going to drop at some point, but the improved performance thus far is the most encouraging sign that he can be at least a viable starting outfielder in the big leagues and for your fantasy roster. 

It's been a rough season for starting pitchers. Some of the attrition was to be expected coming off the shortened 2020 campaign, but the amount of turnover has caused real-world general managers and fantasy managers all sorts of problems trying to fill out a rotation. 

Huascar Ynoa has dealt with his own injury issues already this season. The Atlanta Braves activated their right-hander off the injured list on Tuesday. He missed three months with a fractured throwing hand suffered from punching the dugout bench after a poor start against the Milwaukee Brewers on May 16. 

Prior to the injury, Ynoa was having a very good season with a 3.02 ERA and 50 strikeouts in 44.2 innings. The 23-year-old didn't show any rust in his first start back on Tuesday night. He allowed no runs on three hits with four strikeouts in 5.1 innings against the Marlins. 

Even though it was a short start as the Braves continue to ease him back into things, Ynoa also generated nine swings-and-misses on 80 pitches. Eight of those came on his slider, and his fastball velocity looked good with an average speed of 96.5 mph. 

His primary competition will be against the National League East. The Marlins, Philadelphia Phillies, New York Mets and Washington Nationals all ranked 16th or worse in runs scored. 

Given how volatile pitching has been for every team all season, Ynoa seems like a good buy-low bet to be a difference-maker for the stretch run. 

In an otherwise lost season for Cleveland, Cal Quantrill has quietly been a pleasant surprise for the team. 

After spending the bulk of his career as a reliever, including the first two months of this season, Quantrill has made a successful transition to Cleveland's rotation. Injuries to Shane Bieber, Aaron Civale and Zach Plesac necessitated his move to becoming a starter. 

Since being stretched out to handle a traditional starter's workload, Quantrill has looks like another developmental success story for a Cleveland organization that consistently turns out high-level starting pitching. 

In nine starts since July 4, Quantrill has a 2.41 ERA and .627 OPS against in 52.1 innings. The right-hander isn't a big strikeout pitcher, but he has done a good job of keeping the ball on the ground. His line-drive percentage is a career-high 24.6 percent, but his fly-ball rate (31.1 percent) and hard-hit rate (27.0 percent) are the lowest marks of his career. 

Another factor working in Quantrill's favor, as is the case with Ynoa, is pitching most of his games in a division without a lot of good offenses. The Chicago White Sox are the only AL Central team that ranks in the top 10 in runs scored. 

Cleveland still has 22 games left against AL Central opponents, plus three games against the Texas Rangers from Tuesday through Thursday. Quantrill has a realistic chance to finish 2021 with an ERA around 3.00 and a respectable 1.25 WHIP.