INDIANAPOLIS – The Colts are back at home Sunday for the first time in the regular season and the first time since Andrew Luck’s shocking retirement broke in the fourth quarter of the preseason game against the Chicago Bears.

Indianapolis is coming off of a tough, hard-fought win over the Titans, and the Colts face off against the Falcons at 1 p.m. Sunday (WTTV) at Lucas Oil Stadium. Atlanta is coming off of its own bounce-back win, a 24-20 victory over Philadelphia on Sunday night.

Facing off against a fairly unfamiliar opponent, here’s what to watch in the Colts’ home opener Sunday:

1. Any time Adam Vinatieri is on the field

The greatest kicker of all time has looked like anything but in the first two weeks, and after the Colts tried out six kickers this week, the pressure is on.

2. Bobby Okereke and Anthony Walker

A concussion will keep Darius Leonard out of action against the Falcons on Sunday, taking away the tackler at the end of the funnel for the Indianapolis defense. Walker will likely slide over into Leonard’s spot, and the rookie Okereke steps into Walker’s spot in the middle. Facing off against an Atlanta offense that has one of the NFL’s better receiving backs in Devonta Freeman.

3. The Colts’ plan to slow down Julio Jones and Calvin Ridley

Jones is the headliner, but it’d be a mistake to sleep on Ridley, who has 12 catches for 169 yards and two touchdowns in the first two weeks of the season. Under Matt Eberflus, Indianapolis isn’t likely to leave a cornerback on an island with an all-out blitz in a key situation like the Eagles did on Sunday; the Colts have to limit the big plays from both receivers if they’re going to keep Atlanta in check.

4. Indianapolis run defense

It has been shaky through the first two weeks — the Colts are giving up 5.5 yards per carry, a figure that ranks 27th in the NFL — gets an Atlanta run game that has been just as shaky, even with Freeman healthy and in the backfield. Freeman is averaging just 2.2 yards per carry, and the Falcons have rushed for just 65 yards per game, 28th in the NFL. The Colts need to keep that trend going; putting Matt Ryan in 3rd-and-long is the way to force him to make mistakes.

5. Ryan is going to give the Colts secondary some chances for big plays

The Falcons passer has thrown five interceptions in the first two games; Indianapolis has one pick, the sublime one-handed grab by Malik Hooker in the opener against the Chargers. Sometimes the best way to beat an explosive offense is to force it into turnovers, and when Ryan takes chances, the Colts have to be able to take advantage.

6. Kemoko Turayis healthy again

That's good news for an Indianapolis pass rush that is tied for second in the NFL with eight sacks through the first two weeks. Atlanta has been shaky at times on the offensive line — rookie right tackle Kaleb McGary is playing through injury — and the more the Colts hit Ryan, the more likely he’ll be to make a mistake.

7. Falcons' passing game

Atlanta’s big-play receivers get the attention, but theFalcons passing game is good because they also have players who can exploit the middle of the field like Freeman, tight end Austin Hooper and wide receiver Mohamed Sanu. Two weeks ago, the Chargers moved the ball by throwing underneath and over the middle; Indianapolis has to make plays in that area, the way the Colts did against Tennessee.

8. Colts tackles must set the edge

Unlike the Titans, the Falcons get most of their pressure with the front four, and Atlanta is inconsistent off of the edges with Vic Beasley, Takkarist McKinley and Adrian Clayborn. From that perspective, this game will come down toAnthony Castonzoand Braden Smith winning matchups on the edge, where Castonzo has been very good in the first two games.

9. Colts interior play vs. Falcons beef

Atlanta is one of the few teams that employs two space-eaters at nose tackle, two massive anchors in Grady Jarrett and Tyeler Davison surrounded by small, fleet players at every other position. If the Indianapolis offensive line is going to dominate the line of scrimmage the way the Vikings did in the opener, Ryan Kelly, Mark Glowinskiand Quenton Nelsonmust dominate the day against Jarrett and Davison.

10. Taking shots in passing game

The Falcons’ speed at linebacker is likely going to force Jacoby Brissettto make throws down the field, the intermediate to deep throws the Chargers and Titans took away. Atlanta’s tandem of Deion Jones and De’Vondre Campbell, plus strong safety Keanu Neal, closes hard and fast, limiting yards after the catch.

Insider:Colts, Brissett confident big plays in passing game will come eventually

11. Group effort on the ground

Marlon Mack has been great through the first two weeks, but if he’s going to play at this level the entire season, the Colts are going to have to give Jordan Wilkins and Nyheim Hines a few more carries per game. Mack has 45 carries already; the good news is Wilkins was deadly in relief of Mack against Tennessee.

12. Young receivers stepping up

Deon Cain and Parris Campbell have flashed the ability to be a bigger part of the passing game. Cain made a key back-shoulder grab in Los Angeles and beat Tennessee’s secondary deep last Sunday; Campbell’s speed was obviously a weapon on his touchdown against the Titans. Indianapolis hasn’t thrown it much, but at some point, the Colts are going to need the two young receivers to be more involved than they have been.

13. Screens keep 'em honest

Speedy defenses like Atlanta’s — and the one in Indianapolis — are often susceptible to screens, but the Colts have had mixed success with the play this season. Whether it’s in the screen game or other routes in general, third-down backNyheim Hineshasn’t done much in the passing game so far. He could play a key role on Sunday.

14. Finding T.Y. mismatch

T.Y. Hilton has been excellent in the first two weeks, and the big-bodied, long-levered cornerbacks the Falcons favor could be a good matchup for the veteran receiver, given his quickness. Desmond Trufant is very good, and he’s got two interceptions already, but Hilton’s ability to change directions as given good secondaries problems in the red zone two weeks in a row.

15. Make special teams special again

The Colts’ problems covering kickshave been lost a little among Adam Vinatieri’s struggles, but Atlanta return man Kenjon Barner is the kind of player who could take advantage. Indianapolis ranks 31st in the NFL in kick coverage and 25th in covering punts, and Barner has the speed to make the Colts play if those problems continue.

Follow IndyStar Colts Insider Joel A. Erickson on Twitter at @JoelAErickson.