Concerns over Jeremy Newberry’s health and his ability to practice and play on a regular basis could lead the 49ers to ask the two-time Pro Bowl center to restructure his contract. Newberry had surgery to repair damage in his degraded right knee joint in December. He hopes to resume practicing with the team, probably on a limited basis, when the 49ers open training camp late next month. Though Newberry said recently that his goal is to play in all 16 games this season, the 49ers remain uncertain about his ability to meet that goal and the team would be reluctant to commit to his $3.5 million salary unless club officials are pretty sure he’s healthy enough to make it through the year.