Ever since Seth Lugo established himself as one of baseball’s best relief pitchers, the Mets have insisted that, despite how Seth sees himself, Lugo is in fact a reliever. When asked, the right-hander has repeatedly told the New York media that he wants to be a starting pitcher again. Now, with the Mets’ backs against the wall, Lugo is getting his wish.

But he shouldn’t be.

Before it was postponed due to two positive COVID tests, Lugo was supposed to start last night against the Marlins in place of Steven Matz, who has had three consecutive explosively bad starts against NL East rivals. After his previous start, a six-run outing in Philadelphia that started off promisingly, Luis Rojas would not commit to Matz getting another turn through the rotation. In theory, this is the right move. The Mets have lost all five of Matz’ starts this season, with Matz himself being on the hook for four of them. The final three have been catastrophic. He has an ERA of 9.00 in 23 innings and has been worth -0.3 fWAR.

But in practice, the Mets really have no other option than to let Matz figure it out. The rotation is in utter shambles. In the past two weeks, Michael Wacha and David Peterson have joined Noah Syndergaard and Marcus Stroman on the shelf. Thankfully, Jacob deGrom tossed six strong frames against the Marlins on Wednesday to quell any doubts that he would not be his normal self after getting scratched last week in Philadelphia. Robert Gsellman has already been inserted into the rotation, as has Corey Oswalt. If not Matz, who is the next man up? Erasmo Ramirez? I wish.

It’s going to be Seth Lugo.

Why shouldn’t Lugo get a crack at the rotation? We know he’s a great pitcher. He’s posted ERAs below 3.00 each of the last two seasons out of the pen, and he’s got a five-pitch repertoire more befitting of a starter than of a high-leverage reliever. Advanced stats and statcast metrics love Lugo. If he can get outs at an elite level out of the bullpen, then it makes sense he could be a dependable starter if stretched out.

But it is not that simple. Lugo is a far more effective reliever than he ever was as a starter. Lugo last started in 2018. He made five starts compared 49 relief appearances that year. In his relief outings, he pitched to a 2.31 ERA with a .204 batting average against and a .560 OPS against. As a starter, he pitched to a 3.91 ERA while those rate stats jumped to .255 and .698.

Let’s take a bigger sample size. in 2017, Lugo started 18 games. In those games, he had a 4.76 ERA with a .286 average against and a .772 OPS against. Those numbers would only be a minimal improvement over the performance Rick Porcello has given the Mets this year. Lugo is the type of pitcher who benefits from his opponents only seeing him once or twice through the lineup. He gave up a whopping opponent OPS of .918 third time through the lineup in 2017.

And we cannot forget that Lugo is pitching with a partial tear in his UCL. He has been since he was diagnosed with the tear in April of 2017. He opted to rehab it and pitch through it, rather than fix it with Tommy John Surgery. As a result, the Mets are extremely cautious with Lugo’s usage. Even as a reliever, he rarely throws on consecutive days, and they do not push him past 30 pitches often. Throwing Lugo for even twice that amount of pitches while in the rotation feels like tempting fate.

But probably the best argument against Seth Lugo as a starting pitcher is Wednesday’s game in Miami. The Mets won 5-3, but they did everything in their power to lose that game. Jacob deGrom threw six shutout innings and left with the lead. Jeurys Familia relieved him and looked shaky. He gave up a hit, a walk, and a run in his third of the inning. Justin Wilson bailed him out by finishing the frame.

But in the eighth, with the Mets leading by two, Luis Rojas opted not to use Lugo. Instead of using an elite reliever who was capable of locking down the final two frames, Rojas turned to reclamation project Dellin Betances. The four-time All-Star has not yet resembled the Dellin Betances who struck out at least 13.5 batters per nine for five consecutive seasons across town. And last night, watching him pitch felt like watching the baseball version of Weekend at Bernie’s. Simply put, Betances looked cooked. He was charged with two hits, a walk, and two runs in two-thirds of an inning.

If Lugo is indeed a starter from this point forward, Edwin Diaz needs to step up. Diaz has looked significantly better than he did last season. He has a 2.53 ERA with 24 strikeouts in 10.2 innings. At times, he has looked absolutely incredible.

For example, in the ninth inning, after Michael Conforto had given the Mets the lead again with a two-run blast, Diaz struck out Monte Harrison and Jesus Aguilar on three pitches each, and finished off Corey Dickerson with a nasty backdoor slider. It resembled the Edwin Diaz we were promised when he came over from Seattle. It was not the Edwin Diaz that relieved Betances in the eighth. That Edwin Diaz came into a bases loaded situation with a one-run lead and walked Logan Forsythe, a .138 hitter for the season, on five pitches to tie the game. All of this happened while Lugo sat in the bullpen and watched helplessly.

The Mets’ bullpen is not good enough without Seth Lugo to survive without Seth Lugo. If the team is certain Lugo will remain in the rotation, we should prepare ourselves to see Seth get hit harder than we’ve become accustomed to. And, we should prepare ourselves for more stressful, gut-wrenching late innings like Wednesday.