Sources: Patrick Chung has surgery

FOXBOROUGH, Mass. -- New England Patriots safety Patrick Chung underwent surgery on his right thumb this week after injuring it Sunday against the San Diego Chargers, according to two sources.

It is unclear how the surgery will affect Chung's availability for Sunday's road game against the Buffalo Bills and beyond. Chung did not practice Wednesday.

With the Bills scoring a league-high 79 points through two games and operating a spread offense that attacks down the field, losing Chung would be a blow for the Patriots. The third-year veteran out of Oregon is second on the team with 14 tackles and was emerging as the team's top safety this season. He also serves as the personal protector on the punt team and plays on kickoff coverage.

Second-year player Sergio Brown (one career start) and four-year veteran Josh Barrett (five career starts) are next on the safety depth chart, followed by five-year veteran James Ihedigbo (no career starts).

Barrett has been playing with a cast over his right thumb.

Chung, a 2009 second-round draft choice (34th overall), injured the right thumb in the third quarter of Sunday's game against San Diego. The injury appeared to occur on a third-down play in which he jammed tight end Antonio Gates at the line of scrimmage, after which Chung was seen looking down at his right hand while shaking it in the air. He stayed on for one more play before taking himself out of the game and ultimately heading to the locker room for tests. Chung returned to the game later in the fourth quarter with a cast over the thumb.

Safety was one of the team's deeper positions in the preseason, but that was before the Patriots released veteran James Sanders and 2007 first-round draft choice Brandon Meriweather.

Mike Reiss covers the Patriots for ESPNBoston.com.