With a 3.00 ERA, the Boston Red Sox finished the regular season with the best bullpen in baseball. For much of the season, that bullpen was anchored by a four-headed monster of Justin Slaten, Tyron Guerrero, Garrett Whitlock, and Aroldis Chapman. 

However, in the waning weeks of the regular season, the best bullpen in baseball has been hit by the injury bug. Slaten was ruled out for the season after receiving a PRP injection in his right elbow. Ahead of Sunday’s regular-season finale against the Chicago Cubs, the team placed Guerrero on the injured list with a right shoulder strain, keeping him out for at least the first two rounds of the postseason. 

With Guerrero now set to miss the first two rounds, the pressure is on these relievers to step up in his absence: 

After being acquired in a trade deadline day deal with the San Francisco Giants in exchange for former top prospect Marcelo Mayer, the 28-year-old left-hander made 10 appearances before allowing his first earned run.

However, it's been rough sledding for Miller lately as he's allowed seven earned runs in his last nine appearances and six in his last five. Miller attributed his struggles to a mechanical issue he was working through, and in his final regular-season appearance on Thursday against the Guardians, he seemed to have things figured out as he struck out the side in a scoreless inning of relief. 

Guerrero had been serving as the primary seventh-inning man against right-handers for manager Chad Tracy, with Miller being the man if there was a pocket of left-handers. With Guerrero on the shelf, Miller will likely be the choice in any situation if Boston has a late lead. 

It was an up-and-down regular season for the 31-year-old right-hander. In his first 48 appearances, Weissert posted a 3.97 ERA in 45.1 innings pitched, struggling in particular when taking over in situations with men already on base, allowing 13 of 29 inherited runners to score, which, at the time, was the third-most among all relievers.

However, after a brief trip to Triple-A Worcester on Aug. 7, Weissert returned to the big-league roster on Aug. 13 and has pitched well since, allowing only two earned runs in 15 appearances, stranding seven of nine inherited runners. 

Weissert becomes the next man up in high-leverage spots when a right-handed pitcher is needed in high-leverage spots. 

The 27-year-old Bello excelled upon rejoining the Red Sox in a bullpen role on July 12, posting a 1.98 ERA as a reliever, the 12th-lowest mark among all qualified relievers. With Guerrero on the injured list, the Boston bullpen becomes incredibly lefty-heavy, especially if Garrett Crochet returns for the postseason. As a result, Bello may take on more of a true reliever role, rather than the bulk role he had taken on for much of his time in the pen. 

In addition to excelling in a relief role, Bello boasts a strong track record against the New York Yankees, whom the Red Sox will face in the wild card round, posting a 2.73 ERA over 69.1 innings. 

However, shifting Bello to a traditional reliever role would likely require rookie left-hander Jake Bennett to make the postseason roster, taking over Bello's bulk role and leaving Boston's Game 1 starter for the divisional round up in the air. Of course, the team would have to beat New York for that to become a problem, and thus one worth figuring out if and when you get there.  

The Red Sox and Yankees will face off in game one of the best-of-three wild card series on Tuesday night at Yankee Stadium. Likely American League Cy Young Award winner Cam Schlittler (14-6, 1.95 ERA) will get the start for New York. Boston has not yet named its Game 1 starter. First pitch is set for 8:00 p.m. ET. 

Zach Coe and David Azer are back on the 'Entering Kenmore' Podcast, previewing the Red Sox' Wild Card matchup with the Yankees. Check it out wherever you get your podcasts or in the YouTube player below.