The Chicago Cubs’ bullpen has been labeled as one of the worst in baseball and their biggest weakness throughout their contending window, but the 2021 Cubs’ bullpen is re-writing the narrative, as they have been the biggest strength of the team. Whether the previous idea was fair or not (it wasn’t) is debatable, there’s no debate surrounding this group of arms at David Ross’ disposal. The key pieces to their success have been unexpected, but were they unpredictable? Let’s take a look.
They had their scoreless inning streak snapped at 38.1 innings on Saturday, but they’ve only given up one run in their last 47.1 innings, through Sunday. It’s been a great luxury for David Ross, who has gotten inconsistent, and often bad, starting pitching performances so far this season, as only Adbert Alzolay has been a consistent, solid arm for Chicago.
The Cubs’ bullpen is an interesting group, but I’ll split them up into two categories based on MLB experience. Craig Kimbrel, Andrew Chafin, Ryan Tepera, and Dan Winkler, four of their top-5 guys in relief innings, have all pitched in the majors for years. As for Keegan Thompson, Tommy Nance, and Justin Steele, this is their first breakthrough into the big leagues. Brad Wieck won’t be featured, as he’s only thrown 4.0 innings, but he’s going to be a big piece of the Cubs’ bullpen if he’s given the opportunity.
Cubs’ Bullpen: Veterans
Craig Kimbrel is an MLB legend and a future Hall-of-Famer, but he struggled badly in his first two years with the Cubs. Neither was a normal season for him, as he wasn’t signed until June in 2019, then the COVID-19 pandemic shortened the 2020 season, and many fans held out hope that a routine could get Kimbrel back on track. He’s been unbelievable this year, as he’s pitched 22 innings and given up just two earned runs.
Kimbrel’s stuff has been electric, as he already has a -6 run value on his curveball and -4 on his fastball, which (on a rate basis) are even better than they were in his unreal 2017 season with Boston. Kimbrel’s 42.4% K% would be the 4th best mark of his career, trailing the aforementioned 2017 season, as well as 2010 (when he only threw 20 innings) and 2012 (arguably the best relief season ever). His 0.82 ERA would be the 2nd best of his career, behind just 2010 (20 innings), and his 2.04 SIERA would only be the 6th of his career.
I’ve been comparing Kimbrel to himself, so let me compare him to others. Kimbrel has the 3rd best WAR among all relievers, and among relievers with at least 10 innings pitched, he ranks 14th in ERA, 7th in FIP, 6th in SIERA, 6th in K-BB%, and 6th in K%. Kimbrel’s combination of volume and effectiveness has him as a top closer once again in 2021, which is a great thing to see for Chicago. His bounceback may have been unexpected for many, but most signs pointed to this, as his astronomical 29.7% HR/FB% was bound to go down, and he still had a 3.73 SIERA and 35.2% K% despite a major walk problem.
Andrew Chafin has become a fan-favorite in 2021 after being acquired in a trade midway through the 2020 season. His strikeout numbers aren’t nearly as impressive, but he’s been super reliable so far in 2021 after he only threw 9.2 innings in 2020. So far in 2021, Chafin has a 2.28 ERA, 3.04 FIP, 15.8% K-BB%, and 3.54 SIERA. The peripherals don’t match the ERA, but they’re still solid.
The 30-year-old lefty ranks in the top 10% across the board in Statcast’s expected metrics, as he’s allowed a ton of soft contact, with an average exit velocity against 85.8 MPH and a barrel% of just 3.3%. His sinker and the four-seam combo have been great for him so far, as he has a -2.3 run value per 100 pitches on each pitch. He has a 29.5% CSW% (called strikes + whiffs) and 13.1 SwStr% (swinging strike%) on the year, leading to a 25.3% K%. He’s given up zero runs in his last 8.2 innings, dating back to May 8th.
The 2020 MVP-vote getter has been off to an amazing start in 2020, his second season in Chicago. Ryan Tepera had a great start to his career, as he was a very effective reliever out of the Toronto bullpen from 2015-18. He struggled in 2019, as he had a 4.98 ERA, 6.03 FIP, and 6.6% K-BB%. The Cubs signed him before the 2020 season, and it’s paid dividends so far, as he’s been one of their better relievers in both of his seasons in Chicago.
Tepera’s 2020 season was solid, but nothing special. He had a 3.92 ERA, 3.34 FIP, 3.10 xFIP, 21.3% K-BB%, and 3.51 SIERA. In 2021, he’s been nothing short of spectacular. He has a 2.55 ERA, 2.68 FIP, 2.88 xFIP, 26.1% K-BB%, and 2.45 SIERA in 24.1 innings, and he’s already had a signature outing when he got out of a bases-loaded no-out jam on Sunday Night Baseball in St. Louis to preserve a Cubs lead.
As a reliever, he’s already used five different pitches this year, but he relies mainly on his four-seam fastball, sinker, and cutter. His cutter is his most used pitch, but it’s the worst out of his regularly used pitches. He has a run value of 0 (average) with his cutter, while he has a -4 run value with his four-seamer, and -2 on his changeup, while using it only 32 times. He has a 32.6% CSW%, 17.6% SwStr%, and 34.3% Whiff%.
Dan Winkler has been another solid arm for the Cubs’ bullpen, despite the massive walk problem. Winkler has walked 12.7% of the batters he’s faced this year, but that’s been an issue throughout his career. Each outing, it seems Winkler is at the brink of a blow-up outing, but his ERA is a miraculous 0.54. His peripherals are not so spectacular, as he has an 11.3% K-BB%, 4.19 SIERA, 4.66 xFIP, 3.42 FIP, and 0.0% HR/FB%.
For Winkler, it’s a matter of time before his ERA inflates, but he’s still a solid arm, who is great when he throws strikes. He has an in-zone swing and miss rate of 25.6%, and his cutter is very effective. He throws it 62.8% of the time, and it’s obvious why, as he has a -6 run value, 29.6% Whiff%, and .266 wOBA against it. He has a 24.7% CSW% and 13.5% SwStr on the year, which aren’t great, but he’s getting the job done out of the Cubs’ bullpen.
Rex Brothers have had an up-and-down career to this career, but 2021 is shaping up to be one of his best years. The 33-year-old also joined the Cubs before the 2020 season, after putting up a 7.61 ERA in 23.2 innings for Atlanta in 2017 and 2018. He spent most of 2018 and 2019 in the minor leagues, where he even struggled there. He only made three appearances for Chicago in 2020, putting up an 8.10 ERA and 8.89 FIP, but he struck out 53.3% of the batters he faced in limited action.
So far in 2021, Brothers has been one of the most productive relievers in the Cubs’ bullpen. He has a 3.31 ERA, 2.81 FIP, 3.54 xFIP, 25.0% K-BB%, and 2.90 SIERA. His advanced numbers aren’t far off from last year, but the results are now there too. He only throws two pitches, a fastball, and a slider, but he has a 38.0% Whiff%, 35.0% PutAway%, 31.9 CSW%, and 16.0% SwStr%. His slider has a -2 run value, and just a .178 xwOBA against.
The Cubs’ bullpen may be headlined by Kimbrel and Chafin, but Keegan Thompson has been one of the most effective pitchers of the group. So far in Thompson’s first major league action, he’s thrown 15.0 innings, has a 0.00 ERA, 3.05 FIP, 4.07 xFIP, 4.49 SIERA, and 8.2% K-BB%. For Thompson, it’s the lack of strikes that’s a little concerning. He’s walked 14.8% of the batters he’s faced.
It’s also a matter of time before Thompson starts to give up some runs, but he’s been one of Chicago’s most impressive performances so far. His four-seamer and cutter have been a solid combo, as he has a -1 run value on each, while he has a 25.9% Whiff% on his curveball. He’s also versatile and has the ability to give the Cubs length, as he’s been a starter his entire professional career until now.
Justin Steele, the Cubs’ 2014 5th round pick, has been lurking for years in the Cubs’ minor league system, but he’s made the best of his first major league opportunity. Out of the Cubs’ bullpen, he has thrown 13.1 innings and given up just three earned runs. He’s currently on the IL with a hamstring strain, but in his first 11 major league appearances, he has a 2.03 ERA, 3.94 FIP, 25.0% K-BB%, 2.54 SIERA, and the 50.0% HR/FB% has lead to a very impressive 2.50 xFIP.
There’s an argument to be made that Steele, despite the 2.03 ERA, has still been unlucky. The 25-year-old lefty has given up a negative launch angle (-9.6 degrees), causing his xwOBA against to be just .229. He has a -3 run value on his slider, and -4 on his four-seamer, which is his two clear best pitches. His Whiff% on his slider is 44.4%, and his four-seamer has an unbelievable 48.8% Whiff%.
Tommy Nance has only thrown 5.2 innings, but his stuff is unbelievable. He’s got a 0.00 ERA, 2.05 FIP, 2.66 xFIP, 28.6% K%, 2.82 SIERA, and 0.2 WAR this season. He has a 61.5% GB%, as well as another negative launch angle. He already has a -2 run value on his four-seam fastball and has a 22.2% Whiff% on the season. Nance throws his sinker at 96.3 MPH, with 15.6 inches of horizontal break and 20.8 inches of drop.
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