Updated

Boston Celtics forward Jared Sullinger pleaded not guilty Tuesday to charges he assaulted his girlfriend over the weekend.

Bail was set at $5,000 cash and Sullinger is due back in court Sept. 19.

Sullinger's girlfriend declined to seek a restraining order and he is allowed to contact her by phone or with another person present, according to details provided by a Boston Globe reporter in the courtroom Tuesday for the player's appearance.

According to the reporter, Sullinger is alleged to have pinned his girlfriend to the bed, pushed her and grabbed her phone, smashing it, after she tried to call police. The couple argued Saturday over "perceived infidelity," according to the reporter.

Sullinger's attorney said the alleged victim didn't call police until 10 hours later. Sullinger had flown to Ohio to stay with his parents on a "pre-planned trip," according to the reporter, and returned after police were contacted.

The player turned himself in to police in Waltham, Mass., on Tuesday morning after a warrant was put out for his arrest.

He was charged with assault and battery, malicious destruction of property (the cell phone) and witness intimidation.

"The experience was humbling and embarrassing for me," Sullinger said in a statement about turning himself in.

"Yet I know that this situation has brought both sorrow and embarrassment to my girlfriend, my family, the Boston Celtics organization, my teammates, and my fans. To all of you, I apologize from the bottom of my heart.

"My lawyers have advised me not to discuss the case at this time. But I wanted to immediately and publicly apologize to everyone affected by this situation."

Sullinger, 21, was a first-round draft pick of the Celtics in 2012 and averaged 6.0 points and 5.9 rebounds in 45 games during his rookie season.

A two-time All-American at Ohio State, Sullinger wore a gray Buckeyes T-shirt to court Tuesday, according to pictures of the appearance.

The Celtics said in a statement they were taking the situation "very seriously" and were "disappointed" by the allegations against Sullinger.