The MLB playoff races are heating up, which means your fantasy baseball playoffs are around the corner. After a wild trade deadline and volatile August, there are teams way out of the mix. But that does not mean there are not players to consider on the Colorado Rockies or the Chicago White Sox. The fantasy baseball waiver wire is where you can clinch your playoff spot, so here is who you should pick up for Week 21.

Each of these players is claimed in fewer than half of ESPN fantasy baseball leagues. Whether they are a pitcher or a hitter, they can help you steal the categories necessary to flip your matchup. With playoff races heating up, some teams are making drastic rotation changes. Are any of the late-season callups worth a flyer in fantasy?

Make sure you make your fantasy baseball playoffs by picking up these players from the waiver wire.

Top five fantasy baseball waiver wire pickups for Week 21

Chicago White Sox shortstop Colson Montgomery (12) hits a home run during the fifth inning against the Detroit Tigers at Rate Field
Matt Marton-Imagn Images

Colson Montgomery, Chicago White Sox SS/3b (Rostered: 15.8%)

The Chicago White Sox are in the basement of the American League, but they have some young stars worth picking up. One is Colson Montgomery, who has come up and dominated offensively while playing a solid shortstop. He has ten homers and 36 RBI in 34 games, despite a low on-base percentage.

There was a big injury at shortstop for fantasy baseball managers with Oneil Cruz on the injured list. If you were playing Cruz at shortstop, where he was still listed on some sites despite being solely an outfielder this year, Montgomery is a solid replacement. He won't bring the stolen bases Cruz does, but he hits for a higher average and does have home-run power.

Brady Singer, Cincinnati SP (Rostered: 31.8%)

The Cincinnati Reds are in the thick of the National League Wild Card race, currently sitting as the first team out. They got Hunter Greene back from injury this week, which was huge. But the streaming option for the week is Brady Singer, who has been solid since joining Cincinnati in an offseason trade. He is slated to start Monday against the Los Angeles Angels and over the weekend against the Arizona Diamondbacks.

Singer had a blowup start on July 21 against the Washington Nationals, allowing seven earned runs in 2.1 innings. Since then, he has a 1.96 ERA, and the Reds are 3-1 in his starts. With two non-playoff teams on the docket, this could be a big week for Singer in fantasy baseball.

Sal Frelick, Milwaukee OF (Rostered: 24.4%) 

If you are looking to replace any injured player, anyone from the Milwaukee Brewers would be a good fit. With Oneil Cruz and Milwaukee's Jackson Chourio on the injured list, Sal Frelick is a great option for fantasy baseball managers. He does not play every day, but when he does, he is a great fantasy option. Frelick has played eight games during the Brewers' 12-game winning streak and has a .903 OPS.

The Brewers are blistering hot and have not shown any signs of slowing down. They have taken Chourio's injury in stride and dominated the National League Central for over a month. Frelick is the poster child for Milwaukee's success, with fundamental defense, timely hitting, and great base running.

Ernie Clement, Toronto UTIL (Rostered: 42.7%)

The Blue Jays still hold the American League East, partly because Ernie Clement did not get the memo that he was supposed to slow down. He has continued his career year with a 1.208 OPS and eight RBI since August 1. He also brings positional versatility to your team that could change matchups coming off the bench. Clement can play any infield position in fantasy baseball, which is huge at this time of year.

The Blue Jays have favorable matchups against the Pirates and Marlins this week, which should keep Clement's hot streak rolling. There are a lot of reasons for Toronto's success this season, but Clement has been the unsung hero.

Nolan McLean, New York Mets SP (Rostered: 3.7%)

The New York Mets have gotten dreadful starting pitching during their current slide. Since June 5, David Peterson is the only pitcher on the team to pitch into the sixth inning. And even he has struggled lately, with a dreadful start on Wednesday against the Atlanta Braves fresh on the mind. The Mets are calling up Nolan McLean to join the rotation, and he is worth a pickup in fantasy baseball.

If there is any other Mets starter on your fantasy baseball team, McLean is worth a pickup. Kodai Senga, Sean Manaea, and Clay Holmes aren't providing the stats needed to clinch a playoff spot. If McLean dominates, it could be the difference in your fantasy baseball season.