Insider: Colts show cracks in armor in preseason win

• Preseason finale: Bengals at Colts, 7 p.m. Thursday, Fox

ST. LOUIS – The most significant dress rehearsal of the Indianapolis Colts' 2015 season yielded cracks in the armor. The Colts were good, plenty good, at times in Saturday night's 24-14 win over the St. Louis Rams. But the team nonetheless did little to squash a short list of growing concerns two weeks shy of the season opener.

There's still plenty of work to be done.

What did we see? We saw Frank Gore watching in tennis shoes. We saw Andre Johnson haul in a too-easy touchdown, then promptly take a seat. We saw Art Jones hurt his ankle and take a seat (more on that later).

The first-team offensive line, a week after an ugly undressing at the hands of the Chicago Bears, looked solid early but soured late in the first half. Josh Robinson saw his first significant action against a first-team defense, and made a costly rookie mistake.

"I thought we did some decent things and put some good drives together early," quarterback Andrew Luck said. "Defensively, I thought our guys did a heck of a job. I'm disappointed to end my time out there with a fumble. You can't let that happen. We did some decent things."

As for Luck, he was busy, finishing 12-for-21 for 161 yards and a touchdown, but missed seizing a few downfield opportunities with wideout T.Y. Hilton that would have given the Colts a cushy first-half lead.

The Colts' starters looked good Saturday night – they definitely didn't look great. Here's what stood out:

>> Art Jones. Hurt. Again? Without being overly presumptive, it was one of the last things the Colts needed to see Saturday night: Their $33 million defensive tackle, Art Jones, limping off the field with another ankle injury. The good news: This was Jones' left ankle; a year ago, a high right ankle sprain cost Jones 13 games.

He left early in the first quarter, on the Rams' first series, and was later carted off. His night of work was over.

We're two weeks shy of the season opener, and this is a vital year for Jones. Making matters worse: The Colts' defensive line really needs to step it up, drastically, this season. Losing Jones for an extended period of time would be costly.

>> Pat McAfee, onsides kick master: A year after leading the NFL in successful onsides kicks, the Colts punter pulled off another one. It came moments after the Colts capped their first drive with a 42-yard strike from Adam Vinatieri. Rookie Clayton Geathers recovered McAfee's kick, and four plays later, Andrew Luck fired a bullet to Andre Johnson that resulted in a 32-yard touchdown. Just like that, the Colts were up 10-0.

>> Mixed results for offensive line: The holes were there early, and Luck had plenty of time in the pocket to inflict 166 yards of damage through the air. But the offensive line's overall body of work Saturday night was inconsistent. To be fair, this was coming against a stout St. Louis front-seven. The Colts had just 36 rushing yards in the first half, primarily because there wasn't anywhere to run.

"I think they did some good things," Luck said of the offensive line. "Obviously no one is perfect. I made my fair share of mistakes. We have our things to work on, but I thought they did a great job upfront."

The good:

>> Erik Walden, who continued his strong preseason with an emphatic sack of Rams quarterback Nick Foles early in the second quarter.

>> Andre Johnson, whose 32-yard first-quarter touchdown catch promises to be the first of many from Andrew Luck.

>> Duron Carter, had a pair of nice grabs in the Colts' two-minute drill to end the first half. While it showed progress, Cater had a miscommunication with Luck on an attempted fade route on 3rd-and-goal. Remember: Baby steps. He finished with three catches for 25 yards, his finest outing as a Colt.

>> Jalil Brown: One of the Colts' best defensive players in training camp, Brown snatched a third-quarter interception that led to a Tyler Varga 1-yard touchdown run. Brown has made enough plays to earn a spot on this roster.

>> Adam Vinatieri, who was 3-for-3 on field goals, including from 42 yards and 55 yards.

The bad:

>> Safety Mike Adams yielded a monster touchdown catch in the second quarter, a 44-yard bomb from Rams quarterback Nick Foles to Chris Givens.

>> Andrew Luck, stop trying to tackle players during the preseason.

>> Josh Robinson, who fumbled the Colts' first carry of the second half. Three plays later, the Rams were in the end zone.

>> Bjoern Werner, who was stood up during the Rams' touchdown run that followed Robinson's fumble. It was a telling microcosm of Werner's preseason – entering what figures to be a vital year, he hasn't made many plays of consequence during the preseason.

The Colts improved to 1-2 in the preseason and will close out their exhibition schedule with a home Thursday night against the Bengals.

Call Star reporter Zak Keefer at (317) 444-6134 and follow him on Twitter: @zkeefer.