A left-handed hitter with power, Mahoney opened the season on the 15-day disabled list, retroactive to March 22, with an intercostal strain.
Some progress was made on Wednesday as he played in an extended spring training game, going 1-for-4 with a home run and two strikeouts.
"He's progressing," manager Mike Redmond said. "There is some help."
Next for Mahoney is playing for Class A Advanced Jupiter in the Florida State League to build up game experience.
First base has been an area of concern for Miami, especially after Casey Kotchman was injured in the second game. At Washington on April 3, Kotchman strained his left hamstring, and he went on the DL two days later.
"None of us expected Kotchman to get hurt," Redmond said. "To have a guy over there who played first base every day in the big leagues, it was comforting to have."
Because of Mahoney's retro date, he can be reinstated whenever the club feels he is ready.
In Spring Training, his power was evident as he belted three home runs and drove in eight runs in 30 at-bats.
"When we talked about a guy who could possibly hit behind [Giancarlo] Stanton, he was one of those guys," Redmond said. "He has a lot of pop. We had talked about that in Spring Training, and he just got hurt those last two weeks of Spring Training, and that was it. Had he stayed healthy, he would have made that decision a lot tougher. He was having a good spring."
Since Kotchman went down, Greg Dobbs has seen considerable time at first base. And on Wednesday utility infielder Chris Valaika made his first start at the position at any level.
Ideally, Dobbs is best suited as a left-handed bat off the bench. But the veteran makes it clear that he can play every day, if necessary.
"If they need me, that's what I'm here for," Dobbs said. "I would hope that they don't keep me out of the lineup for the mere fact they don't want to [play me too many days in a row]. I want to be out there. I come to the field prepared to be either playing or to come off the bench."