ARLINGTON -- Dodgers fans might have to worry about their All-Star catcher a little bit longer. Russell Martin has been watching video and hitting extra in the batting cages, but he hasn't discovered what's causing his recent slump.

"I don't know," he said. "It's probably a bit of pitch selection, a bit of bad luck. I'm hitting the ball right at people. My timing may be a little off. I'm just not squaring the ball up."

Entering Sunday, Martin was hitting .107 with no extra-base hits in June. He has posted a .194 on-base percentage this month.

His season stats are off from his career stats, as well. Martin's on-base percentage is a respectable .353 entering play Sunday, but his power is missing. He hasn't hit a home run this season and is slugging .289.

His batting average on the season is .244.

"I think it's creeped into his approach a little bit," Dodgers manager Joe Torre said. "I'm not concerned about the lack of home runs. I'm just waiting for him to hit line drives. The home runs he hits are line drives that go over the fence."

Torre said Martin is more successful when he hits the ball to the middle of the field. Martin said he might have gotten away from that.

"I might be pulling off at times to create something," he said. "You can't think about what you're doing wrong, but only what you're doing right."

His lack of production at the plate also could be compounding.

"He's struggling," Torre said. "You go up there and you lose what you want to do. When you're not getting hits, you're not quiet in the batter's box."

Martin, however, isn't ready to blame his mini-slump on his strenuous duties behind the plate. He has started at catcher in 54 of the Dodgers' 63 games this season.

"Not at all," he said. "It's definitely a heavy workload. Everyone gets to a point where you hit the wall."

This season continues a stretch of rigorous work for Martin at catcher. He collected 514 at-bats at the position last season and 528 the season before. Martin, 26, thinks his young age allows him catch that many games without feeling the effects too much.

Could starting Sunday's game as the designated hitter get Martin going?

"We'll have to wait and find out," he said. "Hopefully, I'll get it back."