Have the Diamondbacks Relievers Been Overworked?

The answer is not as obvious as it may seem on the surface

Handling a bullpen, and reliever workloads is one of the more challenging aspects of a manager's job. The best laid plans can be completely thrown off course by circumstances completely outside the manager's control.  But how workload is measured is not something easily understood by those outside the organization because we simply don't have enough information to make a completely informed judgement. 

Back in 2021 Diamondbacks manager Torey Lovullo outlined some of the factors that go into determining a reliever's workload. 

"We have a really strong process here. The medical team works extremely hard on gathering information and it’s built around how many times somebody is up in the bullpen, how many warmup tosses they take, their overall workload, their built in workload over a 5 day period, over a 10 day period, the total number of pitches thrown in a game and it spits out an equation."   Link 

We on the outside can chart things like games, innings, batters faced, and even pitches thrown in games. However a reliever's workload beyond when they pitch in a game are simply not known to us, so sometimes a pitcher is not used when it might appear he should be available by looking at game data, and other times a pitcher is available despite seeming to be overworked on the surface.  The manager will usually shy away from stating publicly who is available or not for competitive reasons, especially prior to a game. That often leads those of us on the outside, pundits and fans alike, to question or even criticize those decisions despite not having all the information. 

We can and should still pay attention to those factors we know however, so lets dive into it and see what we turn up. First, we'll look at he "on pace" numbers for the D-backs relievers that are currently on he roster.  The team has played 42 games of he 162 game schedule. Simply by taking the workload and multiplying by 3.857 we arrive a he on pace numbers below.

2023 Workload , Year to Date

Note: Jose Ruiz' numbers include four outings with the White Sox and Anthony Misiewicz' minor league outings are included in his total

In 2022 there were just four pitchers in MLB with 76 or more outings and 14 pitchers with 69 or more. On the other hand there were 17 relievers with over 70 innings pitched last year, and no fewer than 75 relievers had 62 or more innings pitched last year.  In other words while he number of games pitched in for McGough, Castro, and Chafin are somewhat high, their innings totals, and therefore pitches thrown in games is not. 

Workload since April 30th

On April 30th the Diamondbacks opted to go with a seven man bullpen, instead of the typical eight. They did this due to a knee injury to Corbin Carroll. Dominic Fletcher was called up, and has been too hot to send back down, so the D-backs have stuck with the seven man bullpen configuration, even though Carroll is fully healthy now. 

Since that date, the D-backs have been fortunate to have gotten much better starting pitching, and much more length than they were getting previously. Leaving two fewer outs on the table for the bullpen to pick up has been a large part of the team's recent success.

Thru April 29th: 28 Games,  5.05 IP from starters, 3.74 IP from relievers

Since April 30th: 14 Games , 5.76 IP from starters, 3.10 IP from relievers

Below is what the workload looks like for the seven relievers just since April 30th. Note I combined Joe Mantiply and Misiewicz workload together. Mantiply came back in late April from the injured list, but had to go back on it recently due to a hamstring injury.

What we can see above is that the seven man bullpen has clearly put a strain on several of the relievers. Pitching in eight games out of the last 14, (Miguel Castro and Andrew Chafin) is clearly not sustainable. Although we can see that Chafin has faced fewer batters and thrown fewer pitches than Castro and Ruiz. Still, Lovullo is going to have to back off that usage. He addressed this recently, stating that he'd like to turn to some of the lower leverage pitchers more often. He's tried that actually, as can be seen with Ruiz. The results have been mixed however. On May 11th he gave up four runs in a 6-2 loss. But then on May 14th he pitched two scoreless innings in a 2-1 victory. 

The D-backs have two more games with the Oakland A's, including a day game this coming Wednesday, before their next off day on Thursday May 18th. That will complete a stretch of 13 games in 13 days. Starting on Friday they have six straight road games, three each in Pittsburgh and Philadelphia and then another off day on May 25th. 

Back on May 4th we discussed the looming position player roster crunch. It did not seem likely the team would be able to avoid going back to eight relievers for much longer. However thanks to the extra length received from the rotation, Lovullo has been able to make it work. It seems like the time is now overdue to make the move. The roster crunch decisions still loom, and won't be any easier, and in fact have been made much more difficult by Dominic Fletcher's emergence and Alek Thomas' slump. 

Whoever the Diamondbacks add to the bullpen will need to pitch better than the options the team has had previously.  Luis Frias, Carlos Vargas, and Peter Solomon have all pitched poorly when given the opportunity at the big league level for the team.  One of those pitchers, or perhaps Justin Martinez might be given a chance soon though to earn a role, or at least fill some innings. Other under the radar options could be to add one of Zach McAllister, Austin Adams, Ryan Hendrix, or Tyler Zuber to the 40-man roster and call one of them up. They've all pitched well for Triple-A Reno. Presumably the team would be most likely to call up a pitcher they feel will throw strikes however. That could be McAllister, as the 35 year old veteran has walked only five batters in 15 innings so far.    

Whatever they choose to do, we should expect a move soon. We'll be sure to update you as soon as get the word from the team.