The San Diego Chargers and Arizona Cardinals silenced doubters on Saturday as they advanced in the National Football League play-offs.

Darren Sproles sprinted 22 yards for the overtime touchdown that lifted the Chargers to a 23-17 victory over the Indianapolis Colts in an American Conference first-round clash.

The Cardinals made the most of their first play-off appearance since 1998, downing the Atlanta Falcons 30-24 in a National Conference contest.

The first round continues today when Miami host Baltimore and Minnesota host Philadelphia.

The Chargers ended the Colts' nine-game winning streak. They ousted Indianapolis from the play-offs for the second year in a row and continued a resurgence that saw them win their last four regular-season games to seize a post-season berth after being counted out at 4-8 in November.

'Everybody was asking me why we were 4-8 ... they're asking me now why we're winning, and I can't put my finger on it either way,' quarterback Philip Rivers said.

'But we have a coach (Norv Turner) who didn't get away from the plan, and he stuck with us when everyone was trying to tear our locker room apart.'

With All-Pro running back LaDainian Tomlinson forced out of the game in the first half with a groin injury - after scoring one touchdown - Sproles picked up the slack for the Chargers.

He rushed for 105 yards and two touchdowns while catching five passes for 45 yards.

His winning run followed a holding call on Indianapolis defensive back Tim Jennings that gave San Diego a first down, and a face-mask call on linebacker Clint Session.

San Diego won the coin toss to start overtime and never gave Colts quarterback Peyton Manning a chance to touch the ball.

Manning completed 25-of-42 passes for 310 yards and one touchdown, but other than a long scoring pass to Reggie Wayne, he struggled in the second half.

Tomlinson said: 'Nobody gave us much of a chance in this game. But the guys in this locker room believed. When you believe, you can get a lot of things accomplished.'

The Cardinals were even happier to prove their critics wrong.

'A lot of people said we were the worst playoff team ever to get in and nobody really gave us a chance,' said Cardinals coach Ken Whisenhunt, whose team locked up their play-off berth early but dropped four of their last five regular-season games.

'We rallied around that and played well. We responded. They took the lead, and we didn't fold up the tent.'

Veteran quarterback Kurt Warner threw a pair of long touchdown passes and Arizona capitalised on mistakes by Atlanta's rookie signal-caller Matt Ryan as the Cardinals ended what had been a fairytale season for the Falcons.

Warner connected with scoring passes of 42 yards to Larry Fitzgerald and 71 to Anquan Boldin, while running back Edgerrin James contributed 73 yards on 16 carries for the NFC West division champion Cardinals.

Arizona took control in the third quarter. Antrel Rolle returned a fumbled snap 27 yards for a touchdown in the opening minute of the second half to put the Cardinals ahead for good 21-17.

Rookie Tim Hightower capped a long scoring drive with a 4-yard run to make it 28-17 with 2:48 to go in the third.

Rookie cornerback Dominique Rodgers-Cromartie then intercepted Ryan's long pass down the right sideline, and early in the fourth defensive end Antonio Smith sacked Ryan in the end zone for a safety that padded the margin to 30-17.

Ryan got the Falcons within 30-24 with a five-yard scoring pass to Roddy White with 4:15 to play. But Atlanta could not get the ball back as the Cardinals ran out the clock.