The above is the Mets’ bullpen ranked by a statistic called “gmLI.” This stat, gmLI, is “game leverage index” — or something — and it measures how important the situations are on average into which the pitcher enters. E.g., if it’s a tied game in the ninth inning, it counts as a high gmLI for that reliever. If it’s a 10-run game in the seventh inning, it’s a low gmLI for the reliever. Average the gmLI for each appearance together, and you get what you see here. A gmLI of 1.0 is league average, higher is more important spots, lower is less important spots.
Anyway, if you look at the above, Terry Collins has gone to Frank Francisco in the on-average most important spots this season — which makes sense, he’s the closer — followed by Tim Byrdak, and then Bobby Parnell and Jon Rauch are about even. In other words: Rauch was already #3 or #4 in Collins’ bullpen hierarchy, so his demotion from the eighth inning maybe doesn’t mean all that much. If he flips with Parnell, Rauch probably pitches in just as important spots, only those spots won’t be in the eighth. Set-up man is just a title.
Also worth noting: The WPA column above is “win probability added,” a stat that answers the question: Did this player increase or decrease his team’s chances of winning? And according to that stat, Tim Byrdak is the only Mets reliever who has increased the Mets’ chances of winning in a meaningful way this season.