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Alex Rodriguez was placed on the disabled list with a strained left calf on Saturday, taking one of the most potent bats out of the New York Yankees' lineup just as the AL East pennant race really starts to heat up.

Rodriguez returned to the lineup for Friday night's series opener against the Seattle Mariners after missing three games with the calf injury. The slugger aggravated it again in his first at-bat, then watched the rest of the game from the dugout.

Yankees manager Joe Girardi said before Saturday's game that he hoped A-Rod would avoid a stint on the DL. General manager Brian Cashman met with team doctors and trainers later in the day, and they decided that it was best to be cautious.

"He's not any worse than he was before, we're just going to play it safe and know we'll have a player in 15 days," Girardi said. "We just all felt, you know what? It's in the best interest to put him on the DL."

Right-hander Ivan Nova will be brought up from Triple-A Scranton/Wilkes-Barre to start on Monday at Toronto. The Yankees will push back the rest of their rotation one day.

Girardi already planned to be without Rodriguez the rest of the series against Seattle, along with a three-game set beginning Monday at Toronto, where the three-time MVP has a hard time with the artificial turf at the Rogers Center — A-Rod aggravated his hip flexor there in June and missed four games.

And there's a day off scheduled for Thursday, before New York wraps up a road trip with three games at the Chicago White Sox.

"We have a built-in day off in five days, so I mean, you look at that as well," Girardi said before the game. "You know, I listen to my doctors and I listen to the training staff and that's what I'll continue to do."

A-Rod has struggled much of the season, at least by his standards, hitting just .265 with 21 home runs. But many of his hits have come with runners in scoring position or other clutch situations, and he leads the team with 97 RBIs in only 112 games.

"I want to be out there," A-Rod said Friday night. "I thought I was beginning to get into a groove. It's obviously very frustrating."

Rodriguez was not in the clubhouse before or after Saturday's game.

Eduardo Nunez made his first career start in A-Rod's place and drove in the go-ahead run in the seventh inning of the Yankees' 9-5 victory over the Mariners. He's expected to split time with Ramiro Pena at third base after getting called up earlier in the week from Triple-A, when Lance Berkman went on the disabled list.

The loss of offensive production at third base is sobering for the Yankees, who began the day one game up on the Tampa Bay Rays in the AL East. Rodriguez has hit 604 homers and driven in 1,803 runs during his 17-year career, while the two guys now taking his place have combined to hit one homer and drive in 27 runs in 135 career games.

"You play 162 games and there's going to be games where some people are out," Derek Jeter said. "You have to pick each other up."