SAN DIEGO – The Bus was back for the Steelers, and Ben Roethlisberger thrust both fists in the air as Jeff Reed's kick beat the Chargers. One problem: Roethlisberger was celebrating on the bench with his left leg wrapped in ice and bandages. Shortly after Roethlisberger limped off the field with an apparent knee injury, Reed kicked a 40-yard field goal with 6 seconds left to give the Steelers a 24-22 win over the San Diego Chargers on Monday night. "I feel great, I feel fresh," Jerome Bettis said after scoring a touchdown in his season debut. "And officially, I am back." Trailing 22-21 in the fourth quarter, Roethlisberger moved the Steelers into San Diego territory and had completed a 9-yard pass to Antwaan Randle El when he was hit on the knee by the helmet of Chargers rookie lineman Luis Castillo. "He laid it on the line," receiver Hines Ward said of the second-year quarterback. "He's lying there hurt on the ground, and he said to me, 'At least we're in field goal range.'" Roethlisberger was replaced by Charlie Batch, who has played only a handful of downs the last three years. Batch handed off three straight times to Bettis before Reed's kick. Roethlisberger ran for one touchdown and threw for another, and Bettis rushed for a TD in his season debut for the Steelers (3-1). San Diego (2-3) had its two-game winning streak snapped. Roethlisberger, whose knee was bent back awkwardly on the hit, was driven off the field on a cart after the final gun. San Diego had gone ahead on LaDainian Tomlinson's 2-yard run with 4:42 left. Tomlinson was stuffed on a two-point conversion attempt that would have given the Chargers a 24-21 lead. Tomlinson extended his NFL record by scoring a rushing touchdown in 17 straight games. Stung by a loss to New England 15 days earlier and coming off their bye, the Steelers bounced back with a crisp game by Roethlisberger and the defense, which made Tomlinson and the rest of the San Diego offense look average. Tomlinson was held to 62 yards on 18 carries. Brees threw his first interception in three games, which set up Bettis' TD run. "That was probably the best defense I've faced as far as the run game in my career," Tomlinson said. Roethlisberger gave the Steelers a 21-16 lead on a 16-yard pass to Heath Miller with 10:30 to go. He was impressive on the go-ahead drive, completing it in only three passes. Starting on the Pittsburgh 38, the second-year pro had completions of 33 and 13 yards to Hines Ward before hitting Miller for the touchdown. Roethlisberger was 17-of-26 passing for 225 yards, with no interceptions. Bettis gained 54 yards on 17 carries. Bettis and Roethlisberger both scored in the second quarter. On third-and-5 from the Chargers' 7, Roethlisberger lined up in the shotgun, took the snap and scrambled into the end zone. His TD came four plays after his apparent 47-yard touchdown pass to Hines Ward was overturned after a challenge by Chargers coach Marty Schottenheimer. Ward made a sliding catch at the San Diego 31, and thinking he wasn't touched by cornerback Quentin Jammer, jumped up and picked his way to the end zone. After watching replays, referee Jeff Triplette ruled that Jammer's hand hit Ward's foot while he was down. Bettis, missed the first three games while recovering from a calf injury sustained late in the exhibition season, scored on a 1-yard run. Bettis' run capped a drive set up when James Harrison intercepted Brees, hurdled Tomlinson and gained 25 yards before being tripped up by Brees. An unnecessary roughness call against Chargers guard Kris Dielman added 15 yards. San Diego pulled to 14-7 on an 11-yard scoring pass from Brees to tight end Antonio Gates with 34 seconds left before halftime. That drive started after a 48-yard kickoff return by rookie Darren Sproles. The Chargers had gone ahead 16-14 on Nate Kaeding's third field goal of the second half, from 41 yards with 11:41 to play. Kaeding also had field goals of 34 and 32 yards in the third quarter. Kaeding's 32-yarder, with 3:54 left in the third, came one play after Willie Williams broke up a pass from Brees to Gates in the end zone.