Shaquille O'Neal out Tuesday

MIAMI -- Celtics coach Doc Rivers said ailing center Shaquille O'Neal "looked terrific" going through an entire practice Monday, but soreness kept him out of Tuesday's Game 2 of an Eastern Conference semifinal series against the Miami Heat.

The Heat beat the Celtics 102-91 to take a 2-0 series lead.

Rivers said O'Neal participated in his first scrimmage work since aggravating the right calf/Achilles injury while playing 5½ minutes against the Detroit Pistons on April 3. It's the only game action he's logged since Feb. 1.

"He can [run during the scrimmage], but it's the after-effects of doing it," Rivers said. "Just watching him walk on the bus, even this morning, the recovery time is just tough for him."

The Celtics have the benefit of three full offdays between Tuesday's Game 2 in Miami and Saturday's Game 3 in Boston, which would allow the 39-year-old center more time to heal. But Rivers stressed again that, as soon as O'Neal is ready, he's going to put him on the floor and believes he'll be an impact player.

"Hell, if he told me today he can play, and [team trainer] Eddie [Lacerte] and them said he could play, I'd have no problem playing him," Rivers said. "At the end of the day, unlike all of us, he's big. You know what I mean? When we play him, he's still going to be big. He's still going to be bigger than anybody on the floor. And if that's for two minutes or 40 minutes, you're still big. Height matters."

O'Neal appeared in 37 games for the Celtics this season, and has been plagued by injuries to the right side of his body, particularly the knee, calf and Achilles.

Meanwhile, the Heat were without forward Udonis Haslem for Game 2. Haslem has not played since Nov. 20 with a ruptured ligament in his left foot.

Information from ESPNBoston.com's Chris Forsberg and The Associated Press was used in this report.