MLB Playoff Picture 2021: Most Important Players to Watch in Monday's ALDS, NLDS

Monday marks the final time more than two games will be played on the same day during the 2021 Major League Baseball season. 

The four-game slate that features two clinching situations in the American League gives fans a chance to sit back and watch postseason baseball all day. 

The afternoon and night will be anything but relaxing for the eight playoff participants, though. The Chicago White Sox and Tampa Bay Rays are under the most stress as they attempt to stave off elimination. 

In the National League, Atlanta and the Los Angeles Dodgers are under pressure to defend their home turf and bank off Game 2 road victories. 

Plenty of important plays will be made over the course of Monday's action, but if the following four players step up in some capacity, their respective series could end or feature a major momentum shift.

Austin Riley was Atlanta's most important hitter during the second half of the regular season.

The third baseman used a late surge in the Most Valuable Player discussion to help his team fend off challenges from the Philadelphia Phillies and New York Mets.

Riley extended his power streak into the postseason in Game 2, as he hit a solo home run to extend his team's lead in the sixth inning. 

The 24-year-old went 3-of-8 in Games 1 and 2 against the Milwaukee Brewers, and he should be vital to cracking Freddy Peralta in Game 3 at Truist Park. 

Peralta allowed two hits over six innings in his lone regular-season start against Atlanta on May 16, but he has been a bit shaky of late. He let up seven earned runs in his last two appearances and allowed three or more runs in four of five September starts. 

If Atlanta gets to the Dominican early, it will create a nice cushion for Ian Anderson to work with inside its home stadium.

Riley can be the player who breaks open the contest early from the No. 4 spot if Jorge Soler, Freddie Freeman and/or Ozzie Albies reach base in the first frame. 

He hit 30 of his 33 home runs against right-handed pitching and he had 66 RBI and a .863 OPS with runners in scoring position. 

Even if Atlanta gets off to a slow start and puts runners on in the middle innings, Riley's bat will be crucial to putting runs across the plate. 

If Milwaukee silences Riley's bat, it will have a much better shot of winning on the road and shifting the series back in its favor. He had a hit in four of six regular-season games and the first two postseason contests against the Brewers. 

If Carlos Rodon feels strong on the mound, the Chicago White Sox will be in a great position to level their series with the Houston Astros. 

That is a big if because of the shoulder fatigue the 28-year-old has dealt with in the last month. He made two starts in the second half of September. 

White Sox manager Tony La Russa admitted on Sunday he and his staff will be monitoring how the fatigue affects Rodon, per James Fegan of The Athletic.

Houston manager Dusty Baker is wary of the threat the pitcher poses on the mound. He told reporters that the test provided by the left-handed hurler will be dependent on "which Rodon is present."

Rodon has pitched 18 innings since August 1. He has not gone more than five innings in any appearance, but he has held all of his opponents to two earned runs or fewer. 

When at his best, he delivers ace-like stuff on the mound. If that version of him shows up, the White Sox stand a strong chance of staying alive. 

Five innings would be an ideal length for Rodon so the White Sox can manage the stress on their bullpen that was called upon to work 7.1 innings on Sunday. 

If that happens, La Russa can go to Ryan Tepera, Aaron Bummer, Craig Kimbrel and Liam Hendriks for an inning each. He could also stretch out Kimbrel since he threw four pitches in Game 3. 

If Rodon's shoulder bugs him and Houston jumps out to an early advantage, the White Sox will be forced to scramble and could work their bullpen thin before getting to Kimbrel and Hendriks. 

The Tampa Bay Rays need a strong offensive performance to stay alive in their ALDS series with the Red Sox.

Luckily for the Rays, they face an ideal matchup against projected Game 4 starter Eduardo Rodriguez. He lasted 1.2 innings in Game 1 and conceded six earned runs to the Rays in his last meeting with them at Fenway Park.

Nelson Cruz bashed a home run off the left-hander in that September 7 matchup. He has two career home runs off Rodriguez in 27 at-bats.

If the Rays get to Rodriguez, as they did in September, they will need one of their power bats to come through with a multi-run hit. 

Cruz was acquired from the Minnesota Twins at the trade deadline for situations just like the one he faces on Monday. The Rays will need one or two big hits out of the experienced designated hitter. 

In Game 1, Randy Arozarena walked and Walker Franco doubled in the first inning off Rodriguez. The Rays managed to get two runs off the Boston started through Franco's double and Yandy Diaz's RBI single. 

Cruz could help the Rays pounce for even more first-inning runs in Game 4 to put Boston's pitching situation in a bind. 

Nick Pivetta is most likely unavailable for the Red Sox after pitching four relief innings in Game 3. Tanner Houck threw five frames in Game 2 in relief of Chris Sale. 

Boston may have to turn to Sale in relief of Rodriguez if the Game 4 starter runs into early difficulties. 

Cruz is 12-of-35 in his career against Sale and hit .500 against him in six at-bats in the regular season.

Cruz has the potential to do damage to both pitchers on Monday and that should allow the Rays to send the series back to Tropicana Field. 

Alex Wood is the most important player for the San Francisco Giants in Game 3. 

The 30-year-old faces the unenviable task of trying to match Max Scherzer, but if he does, the Giants could use one or two runs to steal back the momentum in their series with the Los Angeles Dodgers. 

Wood is no stranger to postseason games, as he has 36 strikeouts in 33 career postseason innings from his time with Atlanta and the Dodgers. 

The southpaw gave up a single earned run across 6.2 innings of work in the 2020 postseason with the Dodgers. 

However, Wood has not started a postseason game since Game 4 of the 2017 World Series versus Houston. He allowed one earned run over 5.2 frames in that appearance. 

Since July 1, Wood conceded at least two earned runs in nine of his 13 starts. He allowed three earned runs on six hits on July 20 at Dodger Stadium.

If Wood reduces the damage on Monday, the Giants will be in a great position to pounce for a single run off Scherzer, or to score a go-ahead run late off the Los Angeles bullpen.

If Wood struggles, the Giants could be forced to max out their bullpen while Scherzer dominates and keeps the momentum on the Dodgers' side going into Game 4. 

Statistics obtained from MLB.com.