Scott Tolzien finally proved that he can run the Indianapolis Colts' offense if starting quarterback Andrew Luck misses the Week 1 game at the Los Angeles Rams on Sept. 10.

Tolzien, who sputtered along during the first two preseason games, played with more confidence and was more aggressive during his extended playing time in the Colts' 19-15 victory over the Pittsburgh Steelers on Saturday at Heinz Field.

Tolzien was 7-of-10 for 123 yards while playing into the second quarter. The 123 passing yards surpassed the 91 yards the sixth-year pro totaled through the air over the first two games. The tone was set from the start, as his first pass was a 55-yard catch-and-run completion to receiver Donte Moncrief. That was the start of a five-play drive that ended with a 1-yard touchdown run by veteran running back Frank Gore.

Four of Tolzien's seven completions were for at least 10 yards, including two that went for more than 30, after he relied on a lot of underneath passes in the first two games. His lone significant blemish was when Steelers linebacker Ryan Shazier intercepted Tolzien after baiting the QB on a pass attempt to tight end Jack Doyle.

“I’m pleased with how we started,” Colts coach Chuck Pagano said during halftime of the television broadcast. “We talked about it all week, coming out here playing the first five [minutes]. We got off to a good start ... then get some points on the board with our offense. [We] moved the ball. Unfortunately, we had the one interception.”

Saturday was a confidence-builder for Tolzien and the Colts because they needed to see something out of the offense to give them hope that they can be effective without Luck if he doesn't play against the Rams.

Luck, 27, is still on the physically unable to perform (PUP) list while recovering from January shoulder surgery. The Colts have maintained that he’ll be off PUP by the start of the regular season. The issue is whether there’s enough practice time for him to regain his rhythm and continuity with his offensive teammates.

QB depth chart: Tolzien got all the attention because of his solid play, but Stephen Morris, who entered the game in the second quarter, continued his strong preseason. Morris was 12-of-16 for 143 yards while leading the Colts to a touchdown for the third consecutive game. He has been the Colts' most consistent quarterback in the preseason. Morris is 36-of-51 for 348 yards a touchdown in three games.

When it was starters vs. starters, the Colts looked ...: The defense, while it gave up at least 10 yards on three of its first four plays, limited the Steelers' starting offense to only three points. The biggest difference was Indianapolis' starting offense. After picking up only three first downs and scoring a total of three points in the first two games, the starting unit picked up seven first downs while also scoring 10 points against the Steelers.

One reason to be concerned: The Colts were missing a number of key players Saturday. Receiver T.Y. Hilton, defensive lineman Johnathan Hankins, running back Robert Turbin and safety Malik Hooker did not play. Cornerback Vontae Davis left the game in the first half with a hamstring injury. The injured players will have two weeks to get healthy because none of the Colts’ key players are expected to play in the preseason finale against Cincinnati on Thursday.

Forcing turnovers: Forcing turnovers was near the top of the list when general manager Chris Ballard was putting together the Colts' defense during the offseason. That has worked out so far, with Indianapolis recording at least one takeaway in each of the three preseason games. Linebacker John Simon put an end to Pittsburgh’s first drive with a strip-sack of quarterback Ben Roethlisberger; Colts cornerback Chris Milton ended another with an interception in the end zone. The Colts have forced five turnovers in three preseason games.