But his stay may be short-lived. The Mets have identified him as "an inventory" player, and their plans for him, according to a person familiar with the club's thinking, may not include many games after the return of Ryan Church. And Church's assignment to the disabled list might end before Phillips puts his legs and arms into a Mets uniform.
The club added Phillips to the 25-man roster and optioned catcher Robinson Cancel to Triple-A New Orleans after the Mets' 8-2 win over the Mariners on Wednesday night. Cancel was to have been the player demoted when Church returned.
So when Church does return -- Friday or later in the weekend -- another roster spot will have to be cleared. Two members of the club's hierarchy indicated Wednesday that Trot Nixon wouldn't necessarily be the player eliminated. It could be Phillips.
"We just want to see which one is the better fit -- Nixon or Phillips," one of the Mets' executives said.
Church was hopeful of ending his assignment to the disabled list Friday. If he plays the outfield Thursday in his rehab start with the Class A Brooklyn Cyclones and experiences no aftereffects, he thought he would be activated for Friday's doubleheader. But if he were to serve as the designated hitter Thursday, his return to active big league duty would be pushed back at least one day.
How he will be used Thursday will be determined, he said, by how he feels.
The club executive said Church probably would be held out more day after he felt strong enough to return, thereby giving the club one more day to assess Phillips and Nixon.
Phillips, 31, had been designated for assignment by the Reds on Monday when the club activated Jeff Keppinger from the disabled list. He had appeared in 15 games, none at first base, five at third and two at second.
But he had played first base primarily in four-plus seasons in the big leagues, the first four with the Yankees.
A right-handed batter with a .248 career batting average, he is more productive against right-handed pitching than left-handed; as is Delgado. Phillips has batted .268 in 336 career at-bats against righties and .208 in 163 at-bats against southpaws.
The disparity in Delgado's 2008 performance is not so pronounced. He began the Mets' finale against the Mariners on Wednesday batting .224 with 10 RBIs and three home runs in 85 at-bats against left-handed pitchers and .233 with eight home runs and 25 RBIs in 193 at-bats against right-handed pitching.
But Phillips is a more gifted defensive player. If he remains on the roster, he could spell Delgado at first or replace him in late innings, as Fernando Tatis did Wednesday night.
Marty Noble is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.