BOSTON -- When Ray Allen misses a free throw at TD Garden, it's often enough to draw an audible gasp from the crowd. After all, Allen is nearly a 90 percent free throw shooter for his career and a trip to the charity stripe has often been nothing short of automatic.

Not this postseason.

Playing through painful bone spurs in his right ankle, Allen's shot is uncharacteristically off, both from the line and the rest of the floor. The future Hall-of-Famer missed six of the seven shots he took Monday night, but maybe more surprising was failing to connect on four of his seven free throw attempts while chipping in just six points in a Game 1 loss to the Miami Heat at AmericanAirlines Arena.

It was only the second time in Allen's career that he had taken at least four free throws and finished with less than a 50 percent success rate.

"I think Ray missed four free throws tonight. I don't think we'll ever see that again," said Celtics coach Doc Rivers. "He almost missed three in a row (after being fouled in the first half)."

As Worcester Telegram & Gazette's Bill Doyle noted, Allen is now 18 of 30 on free throws this postseason, and those 12 misses match his regular-season total from the entire 2008-09 season (237 of 249) when Allen shot a career-best 95.2 percent at the stripe.

While the bone spurs have clearly left him hobbled, the shooting woes have still left one of the game's greatest shooters frustrated with an inability to correct the issue.

"I'm just trying to find my balance," said Allen. "I feel good over it, I'm just not in a great rhythm right now. I just know I don't have good timing right now. The shot feels fine. If it's short, I know that I do have less lift on it . I just take it day by day, trying to figure out what I'm dealing with. I do have restrictions. That's why we have a great team here, why we have each other.

"I believe you guys know what I'm dealing with. It's nothing really to talk about. It's like a battle within myself, I have to try to win. It's a daily situation I have to deal with. This is the time I need to be out here to help the team win. When the season's over with, I'll have to deal with what I have to deal with myself, personally. Right now, it's the playoffs and you play."

While Rivers has acknowledged a potential for having to pull Allen if the ankle is affecting his overall play, the Celtics are trying to let him battle through.

"Ray is going to try to figure it out," said Rivers. "We're going to try to figure out a way of even maybe subbing him differently to keep him strong. Honestly, I don't know yet with Ray."