WALTHAM — Friday after practice, Celtics coach Doc Rivers said team captain Paul Pierce is unlikely to play on Sunday’s opening day match-up against the Knicks.  According to Rivers even if trainer Ed Lacerte clears him to play, Pierce will not be in the starting lineup and will only log about 15-20 minutes in the contest. Rivers said the void left by Pierce’s nagging right-heel injury will be filled, most likely, by ninth-year veteran, Sasha Pavlovic.

Pavlovic played 17 games in Boston last season, and was signed late in this year’s shortened training camp. Pavlovic feels better about his role on the team following last season’s stint, and also realizes he has large shoes to fill Christmas day. “I feel a lot more comfortable,” Pavlovic said. “It’s going to be tough with Paul not going, but whenever coach calls my name I’m going to be ready.”

Pavlovic played with three other teams last season, before signing with the Celtics at the tail end of the year. Before last year Pavlovic played one year in Minnesota. Though, he is best known for being a key role player for five seasons in Cleveland, including the 2006-07 team which made a run to the NBA Finals.

The Serbian-born forward said this is the best he has felt since his days in Cleveland. “I’m trying to get back to that level,” Pavlovic said of his time as a Cavalier. ”I have a lot of confidence and my teammates trust me.”

Defensively Pavlovic is challenged with guarding one of the NBA’s best scorers, Carmelo Anthony. “Carmelo is huge,” Rivers said. “I don’t think people realize how big he is.”

Rivers praised Pavlovic’s defensive ability as well, and Pavlovic noted he is no stranger to dealing with Anthony. “I’ve guarded [Anthony] before,” the 6-foot-8 forward said. “I have to make him take tough shots.”

Rivers said he has noticed an improvement in Pavlovic’s game since last season. The coach is confident he will be able to integrate himself appropriately, but doesn’t want Pavlovic to force anything either. “He looks good,” Rivers said. “It’s easier [playing ] with the first unit. What I don’t want to do is have him get to aggressive and turn the ball over.”

Rivers left the possibility of starting Marquis Daniels open, but felt the second unit needed to gain continuity going into the season. “I’d love to keep the second unit in tact,” Rivers said. “[The second unit] really feel each other, and I think Marquis really helps.”

One thing is certain, replacing Pierce is no easy task, especially under the bright lights of Madison Square Garden. Including the playoffs, Pierce averaged 26 points per game last season while playing in New York. This featured perhaps one of his most memorable performances as a Celtic, a 38 point effort where he knocked down six of his eight 3-point attempts in Game 3 of Boston’s first round series against New York.

As players and coaches have reiterated all training camp, the season starts on Sunday — no matter what. “I think you have to start [the season] fast, and you have to stay fast,” Rivers said.

With or without their captain, the Celtics hope to kick things off in high gear.