Bob Thomas, cut by the Bears two weeks ago, kicked four field goals and Billy Sims made his first start of the year an impressive one today as the unbeaten Detroit Lions defeated the winless Los Angeles Rams, 19-14.

Sims, who ended his preseason holdout 1 1/2 weeks ago, carried 25 times for 119 yards and caught five passes for 103 yards, becoming the 13th player in NFL history to rush for more than 100 yards and catch passes for more than 100 yards in a game.

Thomas was acquired to replace Ed Murray, who left camp in a contract dispute. Today, Thomas was four for four, with field goals of 45, 46 and 30 yards in the second quarter and a 33-yarder in the final period.

Vince Ferragamo came off the bench early in the third quarter to replace Bert Jones, who left with a slightly pulled right hamstring, and guided Los Angeles to two fourth-quarter touchdowns. Jones said he could have kept playing, but, "It's no big issue . . . I don't see any reason why I won't start next week."

The Rams drove to the Detroit 27-yard line late in the game, but Ferragamo fumbled when sacked by William Gay with 1:21 remaining; Doug English recovered for the Lions.