NEW YORK -- Last month, the Mets announced their intentions to stretch two relievers out as starting pitchers. The Seth Lugo Experiment has gone swimmingly; Lugo fired a season-high five innings on Saturday night and owns a 1.54 ERA as a starter.

The Robert Gsellman Experiment did not go quite so well. Following four brief and mostly ineffective starts, the Mets announced Sunday that they plan to transition Gsellman back to the bullpen.

“It gives us that breather in the bullpen that can give those guys a little bit more freshness,” manager Luis Rojas said.

The decision is less about Gsellman and more about the Mets’ other options. Now that Michael Wacha and David Peterson are healthy, the team has five clear starters in those two, Lugo, Jacob deGrom and Rick Porcello. That leaves no room in the rotation for Gsellman, who started for the Mets from 2016-17 before becoming a full-time reliever.

Still, Gsellman could have made the decision harder had he pitched more effectively. As a starter, he routinely struggled with both his control and his command, walking six batters in 9 1/3 innings en route to an 8.68 ERA.

“I’m just out of my mechanics,” Gsellman said after his final start. “I’m falling behind. I’m walking the world.”

Gsellman, who utilizes a three-pitch starter’s repertoire, should settle back into a multi-inning role in relief.

“Gsellman can definitely help our bullpen now bouncing back,” Rojas said. “We tried to get some help out of the starting rotation, because we were really in a lot of adversity at the moment. But having Wacha, having Peterson back, and now Lugo stretched out, having the five guys -- we’d rather have those five and take Gsellman to the bullpen where we need a lot of help there.”

Playing the 'hot hand'
Rookie Andrés Giménez started his third consecutive game at shortstop on Sunday, relegating Amed Rosario to the bench. Although Rosario had a three-hit game the last time he was in the lineup, the Mets appear committed to keeping Giménez there for as long as he is healthy.

“Every day, we’re putting out there the team that’s going to give us the best chance to compete and win,” Rojas said.

Rosario owns a .194/.194/.313 slash line against right-handed pitchers this season, compared to a .293/.323/.421 mark for the left-handed-hitting Giménez. The rookie has also proved to be a superior fielder and baserunner, with seven steals in seven chances.

For those reasons, he has supplanted Rosario on what appears to be the long side of a shortstop platoon, even if the Mets are not putting labels on it.

“We talked about staying ready whenever he gets the chance,” Rojas said. “I explained why [Rosario] is not in the lineup, why we’re going with Giménez at times, why we’re going with [Luis] Guillorme at times that he hasn’t been in the lineup. We’re basically matching up.”

From the trainer's room
The Mets announced that rookie pitcher Franklyn Kilome is on the injured list due to a split fingernail on his pitching hand. The team had previously said it optioned Kilome to its alternate training site in Brooklyn.

Kilome, 25, last pitched Tuesday in Baltimore, allowing four runs in three innings of relief.