INDIANAPOLIS — Once Tavon Austin broke free, the Indianapolis Colts couldn’t even slow down the rookie, much less catch him.
Austin, the first-round draft pick with uncanny speed and unlimited potential, scored on a 98-yard punt return and grabbed two long touchdown passes Sunday as the St. Louis Rams ended a three-game losing streak with a stunning 38-8 victory over the AFC South-leading Colts.
‘‘I’ve been patient for eight weeks and, hopefully, it’s my time right now,’’ Austin said. ‘‘I knew the day was going to come. It was just me being patient and me being true to myself. I’m just glad that I had an opportunity.’’
Nobody did more against Indy (6-3) this season — or any time recently.
Austin returned four punts for 145 yards and scored on touchdown passes of 57 and 81 yards, his only two catches of the day. He also returned one kickoff for 27 yards while making the Colts look foolish all day.
Austin’s one-man show started when he backed up and waved off teammates as Pat McAfee’s punt sailed deep into Rams territory. But as the Colts moved into position to down the bouncing ball, Austin reached out and dangerously grabbed it at his 2-yard line.
The Colts didn’t react immediately, apparently believing the play had stopped, and Austin sprinted down the right sideline, avoided one defender and picked up a block on McAfee, and reached the end zone to give the Rams (4-6) a 21-0 lead.
Even Rams coach Jeff Fisher couldn’t believe it.
‘‘I went from saying, ‘Get away, get away, get away,’ to ‘Go, go, go!’ ’’ Fisher said.
Austin later caught a short pass on a drag route over the middle, turned upfield, and avoided two defenders with an inside cut for the 81-yard score. That made it 35-0 — too big a deficit even for the masterful Andrew Luck to overcome.
The Colts just couldn’t get a handle on the 5-foot-8-inch, 176-pound receiver who finished with 310 all-purpose yards and three TDs.
‘‘That was a lot of fun to watch. Tavon, he’s lightning in a bottle when he gets the ball in his hands,’’ quarterback Kellen Clemens said. ‘‘His performance tonight is certainly going to be one for the books.’’
Clemens went 9 of 16 for 247 yards with two scores and no interceptions, hooking up with Austin on the two longest completions of his eight-year NFL career.
The defense was good from the start, too, opening the game with a strip-sack from Robert Quinn. Chris Long scooped up the loose ball and returned it 45 yards for a score. Until scoring their only touchdown, late in the third quarter, Indy had just 181 yards of offense.
Luck was sacked three times and the Rams picked off four passes — three of them by Luck — to win for the first time since Sam Bradford went down with a season-ending knee injury Oct. 20.
For the Colts, it was a miserable performance.
‘‘We just didn’t do anything,’’ coach Chuck Pagano said. ‘‘I take full responsibility for it as the football coach, we did not have this team ready to play.’’
Luck finished 29 of 47 for 353 yards with one TD, though most of that came after the Colts dug themselves into a 38-0 deficit. Indy ran 14 times for a measly 18 yards, 1.3 yards per carry. The defense couldn’t get a handle on Austin or his teammates, resulting in Indy’s worst loss at Lucas Oil Stadium — and its worst home loss since San Diego hung a 31-0 shutout at the RCA Dome on Nov. 29, 1993.
Austin provided all the highlights on a day the Colts would like to forget.
‘‘It is what it is, we got our butts kicked, we’ve got to move on,’’ said Pagano, who will take the Colts to Tennessee on Thursday night.