The Boston Celtics have rarely been entirely forthcoming in regards to injuries. They weren’t open when Kevin Garnett went through the seven stages of “how to fake like a season-ending injury isn’t season-ending,” they weren’t candid when Shaq’s Achilles tendon ended his 2011 season (and ultimately his career), and now there’s Ray Allen, who has missed 13 of the past 18 games with a bothersome ankle.

What we know: The Celtics said Allen was all set to play last week without any limitations, but a simple workout before the game brought on another round of swelling. Jackie MacMullan, one of the most respected sports reporters ever, went on the radio and told us Allen will likely require surgery at some point. When asked whether surgery will indeed be an option at some point, Rivers told reporters he wasn’t sure, but that Allen would know more about that.

The persistence of swelling and the lack of recovery could mean two things: 1) The injury is more serious than the Celtics are letting on, or 2) Allen, like any 36-year old with more than 40,000 NBA minutes under his belt, no longer bounces back from injuries like he used to. Either option is enough for a Celtics fan to worry. When factoring in that Allen has a history of ankle issues, including double ankle surgery that ended his 2007 season prematurely, this could really be something concerning.

Rivers’ own level of concern is growing, and maybe not just because he doubts Allen will return in time for the beginning of the playoffs. Allen has never played off the bench before and could use some time to adjust to his new role, which will likely include more play-making than he’s used to.

Is there enough time for Allen to return to the lineup, get his legs back and make an impact off the bench? Of course. But this ankle situation is becoming more concerning by the day.