TAMPA, Fla. -- While the Yankees continue to wait for news on Alex Rodriguez's health, there were positive signs from Mariano Rivera on Thursday, as the closer threw off a mound without difficulty.

Rivera, 39, worked off a bullpen mound at George M. Steinbrenner Field, throwing 15 pitches from halfway up the mound and 15 from the rubber, increasing his velocity as he neared the end.

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"I was real pleased with what we did today," Rivera said. "The big thing is going to be [Friday], how I feel. It's my first bullpen [session] after a long time, but I expect good things."

With Yankees manager Joe Girardi, pitching coach Dave Eiland, bullpen coach Mike Harkey and trainer Gene Monahan looking on, Rivera said that he was throwing at about 85-90 percent of full speed.

"When you have this type of Spring Training, you don't just get your strength from doing exercises," Rivera said. "Your strength comes from throwing. The more you throw, the better, if there's not pain or soreness."

Recovering from arthroscopic surgery to shave down an AC joint in his right shoulder last October, Rivera had been limited to playing catch this Grapefruit League season. He remains on track to appear in a game within the next two weeks, and Girardi has circled March 17 as the date to shoot for.

"That's what we're planning," Rivera said. "Hopefully, the body and arm will feel as it's been feeling. Every day it's getting better and better, and that's a good thing."

Right-hander Edwar Ramirez also resumed throwing activities after a bout with right shoulder tendinitis. Ramirez said that he would need to throw three or four more bullpen sessions before he could get into game action, but he said he should have enough time to prepare for Opening Day.