In a clutch situation, a closer need to shut the door, not allow the opponent to open and then run through them. The latter is what happened in yesterday’s Mets-Pirates game.

The victim: Edwin Diaz.

Let’s start by looking at his ERA as the season has progressed:
– April: 2.00
– May: 3.97
– June: 2.38
– July: 12.60

Over the past 30 days, his performance based on his ERA has been on the decline.
– Last 30 days: 8.38
– Last 15 days: 12.60
– Last 7 days: 27.00

In particular this season, Diaz’s performance in away games has been worse than in home games.
– Home ERA: 2.45
– Away ERA: 6.75

In home games, his record is 3-1; whereas, in away games it is 0-3. Similarly, in day games, his record is 3-1; whereas, in night games it is 0-3.

Even more surprising are his slash lines for right- and left-handed batters.
– Against right-handed batters: .275/.351/.362
– Against left-handed batters: .175/.303/.222

Diaz is at his best on two-strike counts.
– 0-2: .200 (BA)
– 1-2: .065
– 2-2: .200
– 3-2: .077

With regard to the effectiveness of his pitches, the run value when he throws his slider is -6; whereas, against his fastball it is +6. Run value reveals a pitch’s impact. The lower the value, the better.

Further, when he throws the slider, batters are hitting .180 with a .213 SLG, but when he throws his four-seamer, batters are hitting .268 with a .366 SLG. Those are the only two pitches Diaz has thrown this season with 63.1% of them four-seamers and 36.9% sliders.

Based on the above data, Diaz is at his best when he does not fall behind in the count, throws more sliders than four-seamers, faces left-handed batters, and pitches in home day games.

The data in this post is from espn.com and baseballsavant.com