All the while, they made a contingency plan in the event that Santana will not start on Thursday -- a development that would likely end his season. Should Santana not pitch, Collin McHugh will make his Major League debut in his place, with the Mets continuing to utilize a six-man rotation.
Santana is 6-9 with a 4.85 ERA in 21 starts, though that hardly tells the story of his summer. Pitching for the first time since undergoing anterior capsule surgery on his left shoulder in September 2010, the left-hander began the year 3-2 with a 2.38 ERA over his first 11 starts, striking out 68 batters in 68 innings and throwing the first no-hitter in Mets history on June 1 against the Cardinals.
But he threw 134 pitches in that start and has scuffled since, dropping seven of his last 10 decisions with an 8.27 ERA. An ankle injury pushed Santana to the DL in late July, and he has allowed 14 runs in 6 1/3 innings since returning. Over his last five starts, Santana has gone 0-5 with a 15.63 ERA.
Partly because of that, the Mets wanted Santana to continue pitching in order to finish his season on a high note, starting the lefty perhaps twice more before shutting him down for good. As recently as Monday, the Mets expected Santana to remain in the rotation until rosters expanded on Sept. 1. But Santana threw a bullpen session that afternoon, felt his back stiffen afterward and went for an MRI the following day.
If nothing else, that development has caused the Mets to rethink their plan.
"We're not going to wear him out," manager Terry Collins said.
To guard against the possibility that Santana will not pitch Thursday, the Mets plan to bring McHugh to Citi Field on Major League Baseball's taxi squad, allowing them to activate him in time for Thursday's start. McHugh, 25, is 2-2 with a 2.45 ERA, 52 strikeouts and 19 walks over his last nine starts for Buffalo, and will be on regular rest. Despite lacking the same prospect pedigree as Jenrry Mejia, who was also considered, McHugh turned heads by dominating for Double-A Binghamton over a 12-start stretch earlier this year. He will likely join the club in September regardless.
The Mets have already dismissed the option of reverting to a five-man rotation, preferring to continue giving Chris Young, Jon Niese and Matt Harvey regular breaks to dampen their workloads down the stretch.