Bob Watson, baseball's vice president in charge of discipline, cited Tavarez for "violent and unsportsmanlike actions" during Monday's game against the Devil Rays. Tavarez punched Tampa Bay's Joey Gathright lightly on the jaw after a play at home plate.
The penalty would start next Monday, when Boston plays its season opener, unless the players' association appeals.
"I'm a little surprised," Red Sox manager Terry Francona said in Fort Myers, Fla. "I know they didn't have video so I'm not sure what they're going on. ... It seems like a lot."
Boston general manager Theo Epstein said he didn't know if the suspension would be appealed.
Tavarez is with his seventh team in eight years and has been suspended four times, starting in May 1996 when he threw a pitch behind Milwaukee's Mike Matheny, sparking a brawl. Tavarez was suspended for three games.
He was suspended for five games and fined $1,000 after a spring training melee in 2001 when San Francisco's Russ Davis charged the mound after striking out because he thought Tavarez, then with the Chicago Cubs, had shown him up.
Tavarez was fined $10,000 by the commissioner's office in October 2004 for throwing a pitch over the head of Houston's Jeff Bagwell in Game 4 of the NL Championship Series. Earlier that season, he was suspended for eight days for applying a foreign substance to balls while pitching.
Francona thinks Tavarez's history was probably a factor in the length of the suspension.
"It sure seems like it because that's a pretty stiff penalty," Francona said.