Only hours after the San Francisco 49ers added a starting strong safety on Tuesday, the team bolstered its front four with experience, depth and versatility, signing unrestricted free agent Sean Moran to a three-year contract.

A solid backup who can line up at both end positions and also log some snaps at tackle in a pinch, Moran played the last two seasons for the St. Louis Rams. He signed a three-year contract that is worth $2.375 million annually, and received a $400,000 signing bonus. With veteran Junior Bryant set to either retire or be released after June 1 because of a neck injury, the 49ers were seeking a proven backup lineman.

"Given how difficult it is to find defensive linemen in this league, you're always happy to add a veteran guy to the mix at that position," said 49ers general manager Terry Donahue. "We like Sean a lot and he'll fit in well with what we do."

The team had actually initiated talks with Moran's representatives a few weeks ago, and the two sides spoke in depth at the annual league meetings in Orlando, Fla., last month. San Francisco earlier in the day agreed to terms with strong safety Tony Parrish, an unrestricted free agent from Chicago, who will replace Lance Schulters in the starting lineup.

Moran, 28, is a six-year veteran who played his first four seasons with the Buffalo Bills before he signed with the Rams as an unrestricted free agent in 1999. St. Louis officials had some interest in re-signing him but acknowledged they had to make space for some young veterans already on the roster and pushing for playing time in 2002.

A former Colorado State standout, Moran has appeared in 79 games and started 13 of them. Of those starts, seven came in 1997 with the Bills, when Moran posted career bests in tackles (37) and sacks (4½). For his career, Moran has 78 tackles, nine sacks and two interceptions.

Moran entered the league as the Bills' fourth-round choice in the '96 draft.

Len Pasquarelli is a senior writer for ESPN.com.