SAN DIEGO -- Still bothered by nagging pain in his left foot -- and now also enduring issues with his right foot -- Luis Castillo has descended into something of a platoon with Alex Cora at second base.

Cora got the starting nod over Castillo at second base on Monday against San Diego right-hander Kevin Correia.

"I'm going to probably go that way until Luis starts moving a little bit better on that foot," said Mets manager Jerry Manuel.

If the Mets face several right-handed starters in a row, the switch-hitting Castillo is likely to play against some of them, and he should continue to start regularly against lefties.

But against most right-handed starters, Castillo will sit.

The goal is to provide him with regular rest in the hopes that the nagging bone bruise in his left foot might finally heal.

Though Castillo downplayed the severity of his injury prior to Monday's game, Manuel said that by favoring his right side, Castillo has now caused some discomfort in that foot as well.

It is still possible that the veteran may require a disabled-list stint sometime in the near future.

"We have to keep doing what we're doing, and if it doesn't get any better, then we have to make a decision which way we're going to go," Manuel said. "[If we] decide, 'Hey, this is not benefiting him and it's not benefiting us,' then we have to give him rest, put him on the DL."

Perez reiterates intention to stay with Mets

SAN DIEGO -- Oliver Perez reiterated Monday that he has no desire to work out his struggles in the Minors.

Sent to the bullpen earlier this month, Perez has since made merely three low-pressure relief appearances for the Mets. Though the team has internally discussed the prospect of asking its $36-million lefty to report to the Minors, Perez is under no contractual obligation to do so.

"I've been around here, and I know what I have to do to be better," Perez said.

Asked if Perez was hurting the team by staying in the Major Leagues, manager Jerry Manuel quipped: "Only if we need a long reliever."

"That's a decision that I guess he's earned the right to make," Manuel said. "My job is to manage what I have."

What Manuel has is a lefty having trouble commanding the strike zone or throwing with his old mid-90s -- or even low-90s -- velocity. Now pitching exclusively in low-leverage situations, Perez has become essentially useless for the Mets in close games.

In his only relief appearance of any length Saturday in Milwaukee, Perez walked two and allowed three runs in two innings.

But he maintains that by staying in the Majors, he can help the team.

"I just have to keep working," Perez said. "When they give me the opportunity, I have to be ready."

An opportunity came during Monday's blowout loss to the Padres, with the Mets trailing late. Perez entered with one out in the sixth inning and finished the game, allowing two earned runs on four hits.

Perez would not comment on a published report that his teammates believe he is hurting the team by staying. Manuel, for his part, said that he was unconcerned by any clubhouse drama regarding Perez.

Niese remains in line for Saturday return

SAN DIEGO -- Jon Niese pitched six innings of two-run ball in a rehab appearance with Triple-A Buffalo on Monday, remaining in line to start Saturday for the Mets.

Niese, who walked none and struck out three against Syracuse, has been on the disabled list since May 17 with a mild strain of his right hamstring.

Mets manager Jerry Manuel indicated that, barring a setback, Niese will start Saturday against the Marlins, taking the spot of Fernando Nieve.

Niese was 1-2 with a 4.79 ERA in eight starts prior to the injury.

Dessens likely to see more prominent role

SAN DIEGO -- Elmer Dessens is pitching well for the Mets, and few other relievers are. So if the Mets are in a tight game in the eighth inning, manager Jerry Manuel will likely turn to Dessens.

Jenrry Mejia is no longer in the eighth-inning mix after allowing multiple baserunners in eight of his past nine appearances. Though Mejia has only allowed runs in three of those games, he has put far too many men on base for Manuel to remain comfortable with him in close games.

"I still think there's a little too much traffic once he takes the mound," Manuel said. "He's gotten out of it, but it's still too much."

Dessens, by comparison, has pitched three consecutive scoreless -- and clean -- innings. Though he did allow two runs in his first big league appearance this year, that came against the Yankees, after Dessens earned a last-minute callup and arrived at Citi Field with the game already in progress.