Rondo was suspended for two games after starting a skirmish that sent players sprawling into the seats in a 95-83 loss to Brooklyn on Wednesday night.
Rondo, averaging 12.9 points and a league-leading 12.9 assists, will miss both Friday's game and Sunday's contest at Milwaukee.
The ban, though, might be coming at a good time. The Celtics (8-7) have won five in a row against the Blazers, including eight straight in Boston dating back to Portland's last win there in 2003-04.
Still, Rondo's second-quarter ejection ended his streak of 37 consecutive games with double-digit assists, which ties him with John Stockton for the second-longest in NBA history.
"I play the game the right way. I'm not a dirty player. Sometimes I let my emotions get the best of me, but I have no intention of hurting anybody," Rondo said after practice Thursday. "I go out there and compete every night, and that's how I play the game. I play the game hard; I play the game with an edge. I'm not a trash-talker. I don't play the game dirty. I play hard and when one of my guys are disrespected, I retaliated."
He was suspended twice last season, once for throwing a ball at a referee, and again during the playoffs when he chest-bumped an official while disputing a foul call.
While the Celtics were 10-5 without Rondo last season, they haven't fared as well without their star playmaker in 2012-13.
Boston lost 102-97 to the Nets on Nov. 15 when Rondo sat out with a sprained ankle and lost again Wednesday with Rondo missing most of the contest.
The Celtics, however, held on for a 98-93 win over Utah on Nov. 14 after Rondo left with the ankle injury late in the third quarter.
Veteran guard Leandro Barbosa, who started the Nov. 15 game against Brooklyn, is expected to fill in for the Celtics. He scored 17 points in his start against the Nets, but finished with two points on 1 of 5 shooting on Wednesday.
Boston will continue to rely on Garnett and Paul Pierce, the team's leading scorers. Garnett had 16 points and 10 rebounds while Pierce had 14 points for Boston, which fell into fourth place in the Atlantic Division.
While the Celtics are trying to pick up their third win in four games, the Blazers (6-9) are looking for their first win on their tough seven-game road trip.
Portland suffered perhaps its worst defeat of the season on Wednesday night, an 84-82 loss at Washington that let the Wizards end their franchise-worst 0-12 start.
"You don't want to be the first team, that's very embarrassing," forward Nicolas Batum said.
Batum and Damian Lillard finished with 20 points each for Portland, which fell to 0-3 on its road swing.
Lillard has been a bright spot for Portland, leading all rookies with 19.1 points and 6.1 assists per game. He's also provided the Blazers with a long-distance threat, making 11 3-pointers over his last four games.