The Lions opened the regular season on the road against the Indianapolis Colts, and came away with a close victory. The Lions jumped out to a 14-0 lead before Indianapolis got on the board. Theo Riddick had a 21-yard touchdown run on the Lions' opening drive, and rookie running back Dwayne Washington scored on a 1-yard run early in the second quarter. The Colts got on the board with a 50-yard Adam Vinatieri field goal, but the Lions went up 21-3 on its next possession when Matthew Stafford hit Eric Ebron for a six-yard touchdown pass. Indianapolis closed to 21-10 near the end of the first half after Andrew Luck tossed a two-yard touchdown pass to Donte Moncrief. The Colts got within a field goal early in the third quarter with a 19-yard scoring strike from Luck to Dwayne Allen and a successful 2-point conversion. On Detroit's next drive, Stafford connected with Ameer Abdullah on an 11-yard touchdown pass to put his team back up, 28-18. The Colts scored the next ten points early in the fourth quarter on a 40-yard Vinatieri field goal and a 16-yard scoring pass from Luck to Jack Doyle, knotting the game at 28. The Lions regained the lead on a 13-yard touchdown pass from Stafford to Riddick, but Matt Prater missed the extra point. That allowed Indianapolis to take a 35-34 lead on its next possession, when Luck again connected with Doyle, this time on a six-yard touchdown pass. Detroit got the ball back with 37 seconds left in the game, and on three plays moved into range for Matt Prater's go-ahead 43-yard field goal with four seconds on the clock. The Lions earned a safety on the final play of the game when the Colts were called for an illegal forward pass in the end zone, making the final score 39-35. This was the first time the Lions defeated the Colts since 1997.
Question: How many yards was Theo's first TD?
Answer: 21