Alex Rodriguez placed on 15-day DL

NEW YORK -- Siding with the most cautious approach, the New York Yankees have placed third baseman Alex Rodriguez on the 15-day disabled list because of his strained left calf.

"We are going to play it extremely safe," Yankees manager Joe Girardi said after the Yankees' 9-5 victory over the Seattle Mariners on Saturday.

Rodriguez had been out of the starting lineup four of the past five games because of the injury, but before Saturday's victory Girardi said the disabled list was not an option.

However, after the win, general manager Brian Cashman and Girardi decided not to risk the calf becoming a bigger problem than it already is. Rodriguez now won't return until the first week of September, at the earliest.

If he hadn't played on Friday, the Yankees could have put A-Rod on the DL retroactive to Monday.

When Girardi announced the decision, he said he had not spoken to Rodriguez about it. Rodriguez did not talk with the media on Saturday. On Friday, Rodriguez said he felt "stiffness" in the calf when he swung, but he didn't think it had worsened.

In place of Rodriguez, the Yankees have recalled Triple-A starting pitcher Ivan Nova from Scranton. Nova will start Monday in Toronto. All the other Yankees starters will be moved back one day.

The Yankees are bringing up Nova, who, if effective, they hope can limit the innings of their starters. Phil Hughes is on an innings count. He has pitched 140 2/3 innings this season. He believes his innings limit is around 175 for the regular season, but the Yankees have never revealed the exact number to him or the media. In the postseason, Hughes will have no innings limit. Girardi said that Nova's impact on Hughes' innings count is getting "a little too far ahead."

With Nova up, Girardi said he will look to split up Javier Vazquez and A.J. Burnett, who have both struggled recently. For most of the season, the two have not pitched back-to-back.

"That is something I will look at," Girardi said.

Girardi said he is not inclined to go with a six-man rotation. If Nova pitches well, he could either alleviate Hughes' innings or replace Dustin Moseley in the rotation. Mosely has been starting in place of the injured Andy Pettitte.

"It might be something we have to look at," Girardi said of a six-man rotation. "Sitting here right now, it is not what I'm assuming we are going to do."

On Saturday, Eduardo Nunez, starting at third in place of Rodriguez, nailed his career first hit, a go-ahead RBI single in the seventh. Nunez, one of the Yankees' top prospects, had been mostly a shortstop in his minor league career, but the Yankees had him play multiple positions at Triple-A Scranton/Wilkes-Barre this season so he could serve as a utilityman in the majors. He and Ramiro Pena will play third in Rodriguez's absence.

Oddly, despite the fact that A-Rod is second in the American League in RBIs with 97, the Yankees are 11-0 without Rodriguez in the lineup. They have also averaged 8.2 runs without A-Rod compared to five runs with him.

Andrew Marchand covers baseball for ESPNNewYork.com. You can follow him on Twitter.