INDIANAPOLIS (AP) - Tavon Austin ran free Sunday, and the Colts couldn't catch him.
The rookie returned one punt 98 yards for a touchdown, caught TD passes of 57 and 81 yards and almost single-handedly ended the Rams' three-game losing streak by leading St. Louis to a stunning 38-8 victory at Indianapolis.
It was the Colts' worst loss since a 55-point thrashing at New Orleans in 2011.
The touchdown catches were the only receptions Austin had on his biggest day of the season, and St. Louis (4-6) won for the first time since Kellen Clemens replaced the injured Sam Bradford.
Indy (6-3) lost for the second time at home this season and only the third time in coach Chuck Pagano's career. It ended Indy's two-game winning streak and delayed what could have been a coronation week for the AFC South leaders. They head to Tennessee on Thursday night.
Clemens was 9 of 16 for 247 yards with the two TD passes, and St. Louis wasted no time in setting the tone.
On the sixth play of the game Robert Quinn, the NFC sacks leader, burst through the Colts' offensive line, sacking Andrew Luck and ripping the ball away. It bounced right into the hands of Chris Long, who ran 45 yards for a touchdown and a 7-0 lead.
Austin then returned a punt 18 yards to set up the Rams next score, Zac Stacy's 1-yard TD early in the second quarter.
After that, Austin dominated.
First, he fooled the Colts' punt coverage team by waving off his teammates on a bouncing punt. The small receiver grabbed the ball at his own 2 and sprinted down the right sideline after it appeared most of the Colts had stopped on the play. That made it 21-0.
Then Austin blew past cornerback Vontae Davis, getting wide open for a 57-yard TD pass to make it 28-0 - the longest pass play of Clemens' eight-year NFL career. The personal best didn't last long.
Three plays into the second half, Austin caught a short pass from Clemens while he was running across the field, stopped and turned up field then cut inside to evade two defenders for an 81-yard TD catch and 35-0 lead.
Even Luck, the master of the comeback, couldn't overcome that big a deficit.
He was picked off in the end zone twice and wound up 29 of 47 for 353 yards with one TD and three interceptions - more bad numbers in his second straight start without Reggie Wayne.
About the only thing that went right for Indy came at halftime when Jeremy Inocencio, an American soldier who served in Afghanistan, stepped out of an SUV in the end zone and walked toward his surprised family, who rushed to hug him on the field. It drew tears from his family members and the largest cheer of the day from Indy's home crowd.