Who should be the A’s closer in 2021?

The A’s had a verifiable hydra in the bullpen in 2020. Their relievers combined for 208.1 innings and a 3.64 FIP, third lowest in the majors. But that hydra had its biggest head cut off this offseason. Closer Liam Hendriks, who was worth 5.2 fWAR over the past two seasons, became a free agent at the end of the 2020 season. And with the A’s not extending him a qualifying offer, It is a near foregone conclusion he won’t return to the A’s in 2021. Fortunately, the A’s are just about as well set up as any team in baseball to replace him. General Manager Dave Forst has said that the four men most likely to replace Hendriks are Jake Diekman, J.B. Wendelken, Lou Trivino and A.J. Puk. All four have their positives and negatives. All four would be closers on most other teams. For the A’s, there is no wrong answer. But it’s fun to talk about the pros and cons to every pitcher. No matter the person the A’s appoint as closer, I know the 9th inning will not be stressful come the 2021 season.

Jake Diekman, the longest tenured player in the A’s bullpen, made some waves at the beginning of this season when he revealed that he learned a new slider grip from Pitching Ninja, and started using it in games. And that new grip helped propel Diekman to the best season of his career. In year nine of his major league career, Diekman posted career bests in K%, FIP-, WHIP, and xwOBA. But even before that change in slider grip, Diekman was very good for a very long time. He has a career FIP- of 79, has never had a season with at least 20 IP and an FIP- above 100, a career K% of 28.6%, a career SIERA of 3.51, and since statcast began in 2015, an xwOBA of .295. Diekman is coming off an incredible season and has the longest track record of anybody in the A’s bullpen, so he should be the front runner when it comes to potential closers. But there are a few concerns when it comes to Diekman’s pitching. The first thing to think about is that Diekman is a lefty. With the new three batter minimum rule, a left handed pitcher who can handle righties as well as lefties becomes incredibly valuable.

But it’s a little more cut and dry than that. Assuming A.J. Puk remains a starter, Diekman is the ONLY left handed reliever on the A’s 40 man roster right now, and so far none of their non-roster invitees are left handed pitchers. Management might want to save him for scenarios when they need to get a left hander out, rather than just saving him for the 9th. Another point of concern with Diekman is that he can be described, most generously, as effectively wild. His career BB% of 12.6% is tied for 23rd among qualified relievers since his debut in 2013 and is not trending in the right direction. To go along with his career high K% of 36.9% in 2020, he also had a career high BB% of 14.3%, just a year after posting a career high BB% of 13.8% in 2018, and just the year before he had a BB% of 12.8%. The trend of an increase in BB% is very troubling. Diekman’s BB% is 12.6 since his debut but 13.5% since 2018, the fifth highest rate among qualified relievers among that time . The one comfort is that his K% is also seeing an increase, from 28.0% to 29.7%. That change has helped balance out the rise in free passes, but one must wonder how confident management will be that Diekman can get the outs needed in the end of games without allowing walks to come back and hurt him. The A’s have made moves that seem to indicate they’re not afraid of walks, but let’s wait to see if their in season actions back up their off-season moves.

Prior to the 2020 season, J.B. Wendelken spent the past two years hovering between MLB and AAA. He always performed well, but never seemed to be given a secured spot on the A’s roster. He never appeared in more than 30 games in MLB in a season and threw just 49.1 Major League innings between 2018 and 2019. But in 2020, Wendelken made sure he couldn’t be passed over anymore, having a breakout year and throwing the second most innings of any reliever on the A’s. Thanks to an increase in his slider usage, going from 4.9% in 2019 to 26.2% in 2020, Wendelken saw his strikeout rate jump from 24.9% in 2018 and 19 to 29.2% in 2020. As usual, Wendelken also limited his opponents’ quality of contact. Hitters averaged an 86 MPH average exit velocity, a 31.7% hard hit rate, and just a .314 xwOBACON against Wendelken. The one issue was that his walk rate went up from 7.3% between ‘18 and ‘19, to 10.4% in 2020. That explains why, despite the higher strikeout rate and similar contact stats compared to 2019, his xwOBA increased to .260; still incredibly good.

The crazy thing is that there is still room for improvement with Wendelken. Wendelken’s third most used pitch was his sinker, thrown at a 10.5% rate. It is true that the pitch generates an obscene amount of groundballs. According to Brooks Baseball, since 2018 Wendelken’s sinker has resulted in a groundball 14.3% of the time. That’s not a 14.3% groundball rate when put in play, that’s a 14.3% groundball rate every time the pitch is thrown. The ball is put in play 20.9% of the time. His sinker results in a groundball 68.4% of the time it’s put in play. That is great. When batters swing at Wendelken’s sinker, though, they do not miss. With a Whiff% of just 19.7% since 2018, it is easily Wendelken’s worst pitch at missing bats, and when batters make contact, even when it’s on the ground, the yield for them is great.  With a .401 xwOBA, hitters feast on the pitch. On line drives and fly balls, Wendelken’s sinker goes over the wall 40% of the time, making contact especially dangerous when it’s not on the ground. The high usage of his sinker makes even less sense given that he has another pitch with armside movement that’s more effective: his change-up. Batters do not fare well against Wendelken’s change-up, having just a .257 xwOBA and 80.4 MPH average exit velocity against it. Wendelken is already very good, but with just a simple change in pitch usage, he can become even better. 

For some fans, hearing Lou Trivino’s name thrown around in A’s closer rumors gave them heart palpitations. After all, Trivino is just one year removed from having a 5.25 ERA and 4.53 FIP in 2019. But Trivino’s 2019 campaign was more a result of bad luck than a true showing of Trivino’s talent and skill level. The discrepancy between his wOBA (.333) and xwOBA (.298) was 11th highest in MLB among qualified pitchers. Looking at Trivino’s advanced stats, he has been above average for his entire career. With a .295 xwOBA, a .345 xwOBACON, and a 25 K%, Trivino is better than a lot of people give him credit for. But again, like Wendelken, there is still room for improvement with a change in pitch selection. Unlike Wendelken, though, Trivino’s needed change is much more urgent. Trivino’s stellar 2018 came with him using his cutter 38.9% of the time, the highest usage rate of any of his pitches. But over the past two years, Trivino has thrown his cutter less and less. From 38.9% in 2018, to 33.5% in 2019 and bottoming out at 23.2% in 2020. It’s a troubling development when you realize his cutter is his best non-offspeed pitch. Instead, Trivino has been throwing his fastball and sinker more, which are both worse in almost every way

With Trivino not throwing his spectacular curveball or changeup more to compensate for batters making better contact off his primary pitches, he’s on the verge of a downward trend. In fact, until Trivino corrects this change and starts throwing his cutter more and his fastball/sinker less, it’s fair to not trust him in any high leverage situations at all. Much like a manager must be preemptive in making pitching changes to prevent the opposing hitters from punishing his pitchers, Trivino needs to make a preemptive change in pitch selection before batters start crushing him. 

Ever since A.J. Puk made his debut as a reliever in 2019, some fans have been clamoring for the hard throwing lefty to move to the bullpen full time. With Puk’s injury history, the move makes sense. He’s only thrown 36.2 innings since 2018, and he turns 26 later this year. Time is running out for the former eighth overall pick, but shoehorning him into a relief role seems foolhardy. Puk has the potential to be an impact starting pitcher, with two plus pitches in his fastball and slider, as well as promising secondary stuff. If Puk does come out of the bullpen, it shouldn’t be a permanent move. The A’s also are lacking a fifth starter currently, and it’s hard to imagine that Puk will move to the bullpen while that hole remains. Puk as a closer is a possibility, but it is an unlikely one. 

With bullpens being used more and more, having a good selection of arms available to come in at a moments notice is more important than ever. Perhaps the A’s could even go so far as to not have a closer set in stone and instead be more flexible, using pitchers as the game situation demands. But until then, it’s fun to discuss the pros and cons of each pitcher potentially becoming closer. Even in a confusing and uncertain offseason, the A’s should find a way to build a bullpen as rock steady as ever.