Although Alex Rodriguez’s return to baseball has been peaceful to date, an unresolved matter could threaten the delicate détente between him and the Yankees. Rodriguez hit his first home run of the season on Thursday, and so begins the countdown to what could soon become a contentious milestone.

Thursday’s home run was the 655th of Rodriguez’s career and left him just five away from tying Willie Mays for fourth on the career list. For the last eight years, Rodriguez has been expecting a $6 million payment when he hit that 660th home run, based on a marketing deal arranged at the end of 2007, when he signed a 10-year, $275 million contract with the team.

If Rodriguez’s career had evolved free of controversy, he might already have received the bonus without any fuss, with still more bonuses expected to follow. But in the post-suspension life of Rodriguez, the Yankees say they do not owe him the money and do not intend to pay it. They gave that message to Rodriguez and his lawyer, James Sharp, in a Feb. 10 meeting at Yankee Stadium. According to two baseball officials with knowledge of the matter, who asked not to be identified because they were not authorized to speak publicly about it, the team’s stance has not changed.

Therefore, barring some kind of a negotiated deal, which is possible in the amicable climate that now exists between Rodriguez and the Yankees, the matter could be headed for an arbitration hearing. But the last hearing that Rodriguez was involved in was an embarrassment for baseball, and both sides may want to avoid a repeat.