MIAMI -- At a time the Marlins are making a push in the standings, they're losing valuable players.

On Thursday, outfielder Austin Kearns was placed on the 15-day disabled list with a right hamstring strain.

Outfielder Kevin Mattison was recalled from Triple-A New Orleans to fill Kearns' roster spot. It's Mattison's second stint with the club. He was first brought up on May 10, but sent down four days later after one big league at-bat.

Kearns has been a big contributor in limited playing time. He's batting .375 with three home runs and nine RBIs. He strained his hamstring while scoring from first base on Giancarlo Stanton's double in Tuesday's win over the Rockies.

Bryan Petersen, Chris Coghlan and Mattison are all left-handed-hitting outfielders on the roster.

"We have to have confidence in the guys we brought in," manager Ozzie Guillen said. "We've got Petey and Coghlan up here. Kearns is going to create a little hole against lefties."

Kearns was getting starts mostly against left-handed pitching. The Marlins are hitting just .221 as a team against southpaws.

A right-handed-hitting possibility to play left field now is infielder Donovan Solano.

Solano took fly balls in batting practice on Thursday.

"A lot happens. It's a long season," Guillen said. "I wish I could have them in the lineup. But I don't. I don't worry about that. I worry about the guys we have in the lineup."

Marlins set to keep running, even without Boni

MIAMI -- Missing Emilio Bonifacio for four to six weeks won't slow down the Marlins' running game.

Jose Reyes and Hanley Ramirez continue to take off whenever they can.

"That's a big loss, losing Boni, but we're still going to play the same game, being aggressive," Reyes said. "When me and Hanley get on, we are trying to get ourselves in scoring position. We know Boni is out. Now we need to step up."

Bonifacio, who leads the Majors with 20 steals, went on the disabled list last Sunday with a left thumb sprain. The speedster will undergo surgery on Friday to repair a ligament, and he's expected to miss four to six weeks.

Bryan Petersen, Chris Coghlan and Kevin Mattison can all play center field.

"Obviously, we're losing a big piece, but everybody has got to step it up," manager Ozzie Guillen said. "I expect Coghlan and Petersen to get on base enough to get a shot at stealing bases. I'm not going to say we've got a very fast team, but we can run the bases. When know when to pick our spots to steal bases."

Reyes now has 13 steals, which is tied for the second most in the game. And Ramirez has nine stolen bases.

The Marlins are enjoying one of the best months in franchise history. They've got themselves back in the race.

Reyes is the primary candidate to keep the running game going. The shortstop, after a slow start, is starting to get back into form. He's batting .292 in May after posting a .220 average in April.

"I'm not on the top of my game yet," Reyes said. "I know when I am on top of my game, and being consistent every single day, I think it's going to be better. I know when I start to get on base a lot, we're going to score a lot of runs."

Worth noting

• Brett Hayes made his second straight start behind the plate on Thursday. Manager Ozzie Guillen said he doesn't know if Hayes will play again on Friday. If Hayes hits, chances are he will get more playing time. Regular catcher John Buck is batting .173.

• With Gaby Sanchez at Triple-A New Orleans, Logan Morrison continues to play first base instead of left field. It appears Morrison and Greg Dobbs will do most of the playing at first base until Sanchez is brought back up.

• Dobbs has 79 career pinch-hits and he's one away from tying Kevin Bass, John Cangelosi and Daryle Ward for 33rd place on the all-time pinch-hit list. Dobbs right now is tied with Tommy Hutton, the Marlins broadcaster, according to Stats.