The 2021 MLB season is fast approaching, and because there will be no expanded postseason this time around, playoff spots will be at a premium. Three division winners and two wild-card teams in each league, and that's it. The current postseason format creates a significant incentive to win the division. With that in mind, we're going to preview each division race and break down the potential X-factors between now and Opening Day. Let's highlight the American League West.

For three seasons, the AL West belonged to the Houston Astros. That doesn't appear to be the case anymore. In 2020, albeit a 60-game shortened season, the Oakland Athletics walked away with the division crown, their first since 2013. The Los Angeles Angels should be doing far better than what their last few division finishes reflect and based on their lineup, which now includes Mike Trout and Anthony Rendon. The last time L.A. took home the division title was back in 2014, which was the last time they made the playoffs.

Meanwhile, in the bottom half of the division, there's the rebuilding Seattle Mariners who showed promise with their third-place finish in 2020 behind American League Rookie of the Year Kyle Lewis' performance, and the Texas Rangers, who are seemingly back to rebuilding after failing to be competitive last season.

Now, here is one 2021 X-factor for each AL West club, listed alphabetically.

Houston Astros: No Springer

The Astros will enter the 2021 season without longtime outfielder George Springer who left for the Blue Jays in free agency this winter. Houston made some solid otherwise by keeping Michael Brantley on a two-year deal, signing reliever Pedro Baez and adding right-hander Ryne Stanek and catcher Jason Castro. Despite Springer's absence, the Astros lineup should be able to keep his production with the return of 2019 AL Rookie of the Year and designated hitter Yordan Alvarez

Alvarez, 23, underwent arthroscopic surgery on both knees in August, and has been easing back into action at camp this spring. There's a lot of unknown still, but at the same time, Alvarez's power holds a lot of potential for Houston's offense if he comes back for a true, successful and healthy sophomore campaign. 

The AL West is pretty winnable, but it does feel like it's the Astros to lose in 2021. The club's championship core is mostly intact (although probably not for long as Justin Verlander, Carlos Correa, Zack Greinke, Yuli Gurriel, and Lance McCullers Jr. will all become free agents after next season), and it seems like that's going to be enough to have them enter the season atop the division as the favorites to win it. 

Los Angeles Angels: Pitching

For some of us here at CBS Sports, the Angels were the biggest disappointment this offseason. The club brought in a new general manager, but didn't bring in much else to help the club get in a position to contend. When you have Mike Trout on your team and you he's only played in three postseason games and the last was seven years ago, you'd think there would be far more urgency than what's been shown. 

For the Angels in 2021, the biggest X-factor is going to be their pitching. Last offseason, the Angels lost out in the Gerrit Cole sweepstakes, and this year, they couldn't get Trevor Bauer. Without a true, proven ace in Anaheim, the club really could have used any one of the top free agent starters available this year.

They did sign No. 52 ranked free-agent starter Jose Quintana, and that's fine. But, Quintana didn't pitch for half of 2020 due to a thumb injury, and the remaining Angels starters aren't the most reliable. There's also a lot of unknowns regarding Shohei Ohtani's ability to return as a two-way player in 2021. If Ohtani returns to the mound and struggles or suffers another injury, then the Angels may be forced to decide his future role with the team. Andrew Heaney, Dylan Bundy and Griffin Canning should be solid, but then you have the concerns of how newcomers Quintana and Alex Cobb will perform. 

It's not just the starting rotation that is an X-factor for 2021, but the Angels bullpen -- one that blew more save opportunities (14) than any other team last year -- will also be something to watch. Raisel Iglesias will come in as the club's new closer after he was traded from the Cincinnati Reds in December, Alex Claudio was also brought in this winter as a left-handed specialist. They'll join returning Angels relief pitchers Ty Buttrey, Mike Mayers and Felix Pena. The 31-year-old Pena is expected to be shut down 2-to-4 weeks after he suffered a Grade 1 right hamstring strain during spring training earlier this week, so it's possible the Angels decide to go out and makes some late-spring additions. Free agent Shane Greene is an option.

All of the Angels offseason moves to bolster their pitching appear to be more focused on short-term solutions/low-upsides rather than established improvements, which doesn't boats a whole lot of confidence in the club's status as a contener in 2021, where the postseason is set to revert back to its 10-team format rather than the 16-team from last year's abbreviated campaign.

Oakland Athletics: Bullpen

It would be a huge shock if the Oakland Athletics manage to post the second-best record in the American League again, as they did in the abbreviated 2020 campaign. Oakland possesses talent, but they didn't add any significant pieces to it this winter. In fact, they ended up losing shortstop Marcus Semien and closer Liam Hendriks. There were some additional losses, with several in the bullpen, with the departures of right-hander Joakim Soria and left-hander T.J. McFarland via free agency. 

For 2021, the A's will need their new closer Trevor Rosenthal (signed to a one-year deal) along with the other new relievers, Sergio Romo, Adam Kolarek and Nik Turley, to be enough for the rebuild of this new bullpen. On paper, the club certainly has the makings of a solid bullpen. Still, the additions and overall revamping don't leave a whole lot of margin for error. The bullpen will need to be strong if Oakland is hoping to defend their division title.

Seattle Mariners: Young core development

The Seattle Mariners have some upside for 2021, but the focus will be on the club's young core as the rebuild continues. This team is not yet a playoff team, but they're on their way to returning to the postseason sooner rather than later. If 2020 is any indication, the future looks good for this young core with unanimous Rookie of the Year Kyle Lewis and talented young pitchers, Justin Dunn and Justus Sheffield

The 2021 season should serve as a good time for continued development for top prospects Jarred Kelenic and Logan Gilbert, who both have yet to play above the Double-A level in the minors. Both Kelenic and Gilbert could win spots on the Opening Day roster with good spring performances. Of note when it comes to how Seattle constructs its roster this year will be watching to see how the Mariners front office responds to the offseason resignation of former president Kevin Mather after he openly spoke about service time manipulation. 

Texas Rangers: Offense

Like the Mariners, the Texas Rangers are in the midst of a rebuild. Theirs is just not planned so much as Seattle's. In 2020, the Rangers were expected to be competitive, especially with the 60-game schedule. Instead, Texas finished the shortened season with the second-worst record in the league. The club quickly settled back into rebuild mode after losing more than a third of the games last season, starting with the trade of Elvis Andrus, which was a clear sign that they were moving forward with a rebuild. 

In 2021, the Rangers still have lots of question marks re: their starting rotation, but for their X-factor of choice, we're going with their offense. It's unlikely the Rangers will contend, but if they want to show some signs of promise, or at the very least, keep things interesting in the AL West, they'll need to see improvement from their lineup. In 2020, the Rangers offense ranked for the second-worst in the league when it came to average (.217), on-base percentage (.285) and slugging percentage (.364). So, not great.