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The Cubs returned home Friday from a wildly successful 5-1 road trip and beat the Reds, 1-0. They have moved to 28-22, and the six games over .500 is a season high. 

After entering the month five games out of first place, the discussion around the team was a quick rebuild that included trading Kris Bryant and possibly Javier Báez, Anthony Rizzo and/or Willson Contreras this coming July. Instead, the Cubs are right with the Cardinals toward the top in the NL Central and have won 10 of their last 12. 

They are now 17-7 in May and all seven losses came by exactly one run. 

One might wonder how that happens. Well, common sense dictates that a team is playing good baseball. The offense has generally been very good since about the middle of April, but has only scored 16 runs during the current five-game winning streak. The rotation has been much better of late, but is still a long-term concern. The bullpen has been holding this team together. 

Many Cubs fans would be pretty surprised by this development. The Cubs were 13th in bullpen ERA in 2020 and on the surface level, the Craig Kimbrel deal had been a disaster through the first two years (6.00 ERA, 1.53 WHIP in 36 innings). The collection of relievers in front of Kimbrel was a bit of a motley crew heading into 2021, too. 

That crew hasn't allowed an earned run since May 15. The only run allowed since then came in the 10th inning when the mandated ghost runner from second base scored on a sac fly this past Sunday. The Cubs won that game anyway. 

The numbers from the Cubs' bullpen since May 15: 38 IP, 18 H, 0 ER, 14 BB, 49 K. The Cubs are 10-2 in this 12-game stretch. 

On the year, the Cubs are third in the majors in bullpen ERA behind the Padres and Cleveland at 2.83. 

Kimbrel will get a lot of the credit and he's done a good portion of the heavy lifting. He's actually fifth in WAR on the team behind their four position-playing stars (Bryant, Báez, Contreras and Rizzo in order). In 22 appearances, Kimbrel has locked down 12 of his 14 save chances with a 0.82 ERA, 0.82 WHIP and 36 strikeouts against eight walks in 22 innings. He looks as good as he's ever been and has a swagger about him that says "game over" the second he takes the mound. 

Beyond Kimbrel, though, the Cubs seem to have stumbled into lots of victories. 

  • Andrew Chafin had a 6.52 ERA last season in 15 outings. Through 25 this year, he's at 2.28 with a 0.97 WHIP and 24 strikeouts in 23 2/3 innings. He's mostly served as the primary setup man for Kimbrel. He's also been a fireman, stranding nine of the 12 runners he's inherited (he added two to that total by getting out of a jam Friday). 
  • Dan Winkler was a marginal reliever when the Cubs acquired him before 2020. This season, he has a 0.54 ERA in 16 2/3 innings. 
  • Ryan Tepera brought career marks of 3.66 ERA, 4.31 FIP and 1.18 WHIP into the season. He's at 2.66, 2.82 and 0.72 right now. He's also recently shown a penchant to get out of bases-loaded jams. 
  • Dillon Maples has long had great stuff but also such awful control and command that he couldn't be counted on. He's always going to walk guys, but this season it's a workable 10 walks in 15 2/3 innings (it was 25 walks in 23 1/3 innings before this year in his career). The result? A 1.72 ERA and 1.02 WHIP with 25 strikeouts. 
  • Justin Steele is hurt right now, but he looked the part for his 11 outings. In 13 1/3 innings, he struck out 21 while posting a 2.03 ERA. 
  • Tommy Nance has since debuted -- at age 30! -- with 5 2/3 scoreless innings, including protecting a one-run lead in the eighth Friday. 
  • Brad Wieck, a 6-foot-8 lefty, has thrown three scoreless innings. 
  • Rex Brothers has a 3.00 ERA in 15 innings, but he's also struck out a whopping 27. 
  • Finally, Keegan Thompson is 14 1/3 innings into his rookie year and hasn't yet allowed an earned run. 

That's a deep bullpen, right? I just cycled through 10 dudes! None were big-name free agent signees other than Kimbrel, and he was viewed a bust heading into the year. Some were scrap-heap pickups. Some looked like career minor leaguers. 

Heading into the season, one of the biggest question marks for the Cubs was the bullpen. Right now, it is the backbone of the team and the main reason they aren't even close to having the look of a seller come July. At this rate, they'll be looking to buy starting pitching. It's quite the reversal from the contending team that has so desperately needed bullpen help that it traded a ton for Aroldis Chapman, traded Jorge Soler for Wade Davis and then signed Brandon Morrow and later Craig Kimbrel.