Clayton, 28, was a first-round pick out of the University of Oklahoma in 2005 and spent five years with the Baltimore Ravens, starting at least 10 games every season. He had 234 catches for 3,116 yards and scored 14 touchdowns, including two rushing scores.
His best season came in 2006 when he caught 67 passes for 939 yards and five touchdowns. In 14 games a year ago, including 12 starts, he had 34 catches for 480 yards and two touchdowns.
Spagnuolo, the Rams' second-year coach, thinks Clayton is a good fit.
"Veteran guy," Spagnuolo said. "Has been around the league. Catches the ball well. He's a quick guy. I think he can help these young guys a little bit. It seemed like a pretty good fit for us."
Bradford, the Rams rookie quarterback from the University of Oklahoma, has gotten to know Clayton a little bit over the years in Norman.
"I think he's a very talented receiver," Bradford said. "To see him come out on day one and really have what seemed to be like a great grasp of the offense already. He didn't ask a lot of questions. He just got in the huddle, I called a play and he knew were to go, knew where to line up and knew what to run. I think he's got a lot of speed. I think if we can get him the ball, he can definitely do some things with it."