FOXBOROUGH -- Patriots coach Bill Belichick opened training camp on Thursday with a warning that the team’s roster may continue to change as camp moves forward.

“We’ve had a little roster movement here over the last few days,” Belichick said. “I’m sure there will be a little bit more in the days to come. We don’t have a full roster right now. But if an opportunity comes up that we can find the right guy to finish out, that can add to our roster then we’ll try and do that ... We’re a couple of players under the limit.”

Belichick called newly signed defensive lineman Tim Bulman an active, smart player. He said newly signed tight end Visanthe Shiancoe is a good football player who has contributed well at each stop in his career. The team also cut veteran running back Joseph Addai, who was added in the offseason.

The coach also confirmed that guard Brian Waters is missing from camp. He said that Waters was missing for the same reason he was missing from minicamp. At the time, Belichick said it was a personal reason.

Belichick added it was not a surprise to him that Waters failed to report.

With Addai gone and veteran BenJarvus Green-Ellis having departed in free agency, the Patriots could have a lack of depth and experience at running back. But Belichick didn’t give any indications that he’s worried, or that he’s considering calling former Patriots running back Kevin Faulk (who has said he may not be ready to retire yet).

“We have seven backs on our roster,” Belichick said. “If we add one, then we add one. If we don’t, we’ll go with what we’ve got.”