Boston Celtics guard Ray Allen, who sat out Wednesday's win against the Atlanta Hawks because of swelling in his ailing right ankle, did not travel with the team to Toronto on Thursday in advance of the start of a four-game road trip.

Allen missed six games after injuring the ankle during Boston's West Coast road trip in mid-March. He developed swelling that limited his mobility. An MRI revealed no structural damage in the ankle, but he received a cortisone shot shortly before his return.

Allen has appeared in five games over a seven-day span, but the swelling returned. During Tuesday's win in Miami, he left the bench at the start of both halves to have his ankles re-taped, an indication the ankle was potentially bothering him then. Celtics coach Doc Rivers said he got a call Wednesday afternoon alerting him that Allen wouldn't be available against the Hawks.

"It just swells, I guess," Rivers said. "I don't know. I got a call a little while ago (informing him that Allen would be out). It is what it is. ... I'm just more concerned that this is the second or third time this has happened. So that's concerning."

Rivers said his expectation was Allen would travel with the team and play in Toronto, but him not making the trip is not an encouraging sign about the status of his ankle. The loss of Allen was lightened by the return of swingman Mickael Pietrus, who had missed 17 days because of a concussion.

After one game in a starting role upon his return earlier this month, Allen began coming off the bench in order to allow second-year guard Avery Bradley to run with the first unit. The Celtics are 11-1 without Allen this year.