It’s Time to Answer Questions : NBA playoffs: Can Bird play? How much help will Barkley be? Are the Pistons still hungry?

Larry Bird, who has a real pain in the back, cranked away on the exercise bike at the Boston Celtics’ practice Wednesday, but can he put the pedal to the metal when it matters most?

Then there’s Charles Barkley. Philadelphia 76er Coach Jim Lynam said he will play the condition of his star’s left knee by ear. Can the 76ers win without him?

Too soon for some (those healing) and too late for others (those reeling), the NBA playoffs will open at five sites tonight, with three more series beginning Friday. The best of the best-of-five matchups is probably the one involving two 50-game winners in the West, the Phoenix Suns against the Utah Jazz, but whether that will be the most closely watched is another matter.

Not when you have:

--Bird’s back. The Celtics were 10-12 in the games he missed because of the chronic problems, and Wednesday, after he skipped practice for the third consecutive day on the heels of missing seven of the final eight games of the regular season, no one was saying whether he would be ready for the Indiana Pacers Friday at Boston Garden.

Reports Wednesday were that Bird, 34, has decided to have surgery on the back during the off-season, and that the Celtics are preparing to go without him next season until November or December. Dave Gavitt, the club’s senior executive vice president, said an operation hasn’t been discussed.

--Barkley’s knee. Milwaukee Coach Del Harris has a home-court advantage for the first time in his 12 playoff series when this Eastern Conference matchup begins tonight, but the Bucks’ biggest help will come if Barkley can’t get up to full speed because of the sprained ligament suffered March 31.

“My knee hurts, but I’m ready to go,” Barkley, who averaged 35 points and nine rebounds in three games against Milwaukee, told the Associated Press. “You can put down the same answer from me every day. My knee is going to hurt for the rest of the year.”

Injuries go both ways--the Bucks will be without Dale Ellis because of a herniated disk. They activated Larry Krystkowiak, who has missed all of this season and most of last with a torn-up knee, so the 76ers are expecting another heavy body to lean on Barkley.

--The Pistons’ pride. They will take on the Atlanta Hawks Friday.

There are injuries and talk that Detroit may not be hungry enough after winning consecutive titles, but the playoffs are about defense, and there is still no one who does it better. Those two crowns came while averaging only 100.6 and 101.8 points, respectively, on offense. This year they averaged 100.1.

--The Bull run. Chicago is 7-1 against New York--its opponent beginning tonight--in the past two seasons and is looking more formidable by the day.

This should be something of a tuneup for the Bulls, coming off their best regular season, but much more to New York. There have been reports that John MacLeod is a lame-duck coach and that Patrick Ewing will ask for a new contract starting at $7 million a season, so the longer that summer vacation is delayed, the longer it will be until the ulcers hit.