ST. LOUIS – Prior to Sunday’s game, Detroit Lions coach Jim Caldwell compared St. Louis Rams defensive tackle Aaron Donald to NFL Hall of Famer John Randle.

With more performances like the one he gave in St. Louis’ 21-14 win before a half-filled Edward Jones Dome, Donald may yet one day join Randle in Canton.

A second-year pro out of Pittsburgh, Donald terrorized Detroit quarterback Matthew Stafford from opening snap to final gun, registering three sacks, six quarterback hits and five tackles.

The 6-foot-1, 285-pound Donald was simply too strong, too quick and too good for the interior linemen who tried and failed to keep him out of the Lions’ backfield.

"Our defense made (Stafford) hold the ball a little longer," Donald said. "I’ve worked my butt off during the offseason. The coaches helped me add to my pass-rushing, but I still have things to work on."

Making Donald’s performance more impressive was that the Rams’ defense has been depleted by injuries during a five-game losing streak. The team put end Robert Quinn and safety T.J. McDonald on season-ending injured reserve this week, while linebacker Alec Ogletree has been out most of the year.

But with Donald dominating up front, St. Louis (5-8) kept Detroit off the board in the first half, even scoring the game’s first points on a 58-yard interception return by cornerback Trumaine Johnson.

Jumping in front of wide receiver Calvin Johnson, Trumaine Johnson picked Stafford’s pass over the middle, then used a nice block on the right sideline by free safety Rodney McLeod to reach the end zone untouched with 4:55 left in the first half.

"I’m glad I don’t have to play against our defense," Rams quarterback Case Keenum said. "They are salty."

Keenum and the offense contributed a little help in the second half after managing just 111 total yards and seven first downs through the first 2 ½ quarters while playing their first game under interim offensive coordinator Rob Boras, who replaced the fired Frank Cignetti on Monday.

St. Louis finally found a rhythm on offense after Stafford’s 9-yard touchdown pass to wide receiver Golden Tate tied the game at 7 with 7:35 left in the third quarter. It marched 80 yards in five plays, scoring when running back Todd Gurley dove just over the goal line’s plane on a 5-yard run at the 3:57 mark.

A 49-yard jaunt off left tackle by Gurley, who finished with 140 yards on 16 attempts for his first 100-yard game since Nov. 1, set up his tie-breaking score.

"We did a good job keeping him contained in the first half, but we had some problems with run fits in the second half," Lions coach Jim Caldwell said.

The Rams notched their eventual game-winning score on a 91-yard drive, Gurley finishing it off with an authoritative 15-yard run which saw him make a hard cut from left to right and then dive inside the front right pylon of the end zone for a 21-7 lead with 12:14 left in the game.

Stafford, who finished 30 of 46 for 245 yards, found Tate on a 2-yard scoring strike with 2:05 remaining. Detroit then regained possession when fullback Michael Burton recovered an onside kick muffed by wide receiver Bradley Marquez.

But a bad snap on 4th-and-3 at the St. Louis 46 forced Stafford to chase the ball down about 10 yards behind the scrimmage line. Throwing on the run, his pass sailed wide of tight end Eric Ebron with 1:40 remaining, and a first-down run by Gurley two plays later wrapped things up.

Keenum, starting his first game since suffering a concussion Nov. 22 in Baltimore, went 14-of-22 for 124 yards with an interception. However, Donald and a shorthanded defense meant that Keenum didn’t have to do too much other than avoid big mistakes.

"We had protection issues and then some miscues at the end," Caldwell said.

The Lions (4-9) were eliminated from playoff contention.

NOTES: Detroit TE Brandon Pettigrew (knee) left the game in the second quarter and didn’t return. He had one catch for seven yards. ... St. Louis WR Wes Welker’s 11-yard reception in the fourth quarter was the 900th catch of his career, making him the 20th player in NFL history to accomplish that feat. … The Rams became the first team in five games to rush for more than 70 yards against the Lions.