INDIANAPOLIS -- The defenses continue to get checked off the list one by one, week by week, by the Indianapolis Colts.

Buffalo. Oakland. Jacksonville. And the Tennessee Titans.

These weren't defenses that hovered near or at the bottom of the NFL rankings. Three of the four defenses were ranked in the top 10 when they faced the Colts.

Each one of them thought they had a plan to slow Andrew Luck and the Colts' offense down, only to leave with a loss -- some worse than others.

The Colts don't currently have the longest winning streak in the NFL. They don't even have the longest one in the AFC, but what they are is one of the hottest teams in the league. Indianapolis won its fourth straight game, this time embarrassing the NFL's top-ranked defense in points allowed per game in a 38-10 victory over the Titans on Sunday.

Catching the Houston Texans, who are on a seven-game winning streak, is a tough task for the Colts, especially since they have already lost to Houston once this season. But the Colts are right in the thick of things for the AFC's final playoff spot; they're one of five teams tied for the sixth playoff spot.

"The good news is we're out the hole," Colts coach Frank Reich said. "The reality is there is still a mountain to climb because of the position we put ourselves in. That's just what we have to do, and we have to take the same approach."

Reich is officially a first-year head coach, but his calming demeanor never allowed his team to buckle during its 1-5 start to the season, when things could have gone from bad to worse. The "self-inflicting wounds" many players say cost them early-season games have been replaced with a confident offensive unit, led by a confident playcaller in Reich, that believes it can score on any defense in the league.

"We're playing complete games now," center Ryan Kelly said. "We're not giving games away. This team has shown a lot of maturity."

The way Luck is playing makes it almost laughable that the question over whether he could return to form after missing all of last season with a right shoulder injury was even a topic of discussion.

Luck's teammates describe his desire to return even better than before his injury as an "obsession." The Colts are averaging 36.5 points, and Luck has thrown for 13 touchdowns and just one interception while completing 74 percent of his attempts during their winning streak. He has gone from being in Europe for shoulder treatment and not being in a "good spot a year ago today" to throwing 29 touchdowns, which is second to only Kansas City's Patrick Mahomes' 31.

"I saw a lot of what Andrew went through in the offseason," left tackle Anthony Castonzo said. "A lot of credit to him. Physically, he's probably better than he's ever been. I'm not surprised. That speaks to his work ethic. Everything he was doing was to get back and play at a high level. It's awesome it's paying off."

Luck is the first to not take the credit for anything. He points to the skill-position players making plays and the offensive line doing its job protecting up front. The offensive line has not given up a sack on 214 straight drop backs.

The Titans entered the game giving up an NFL-low 16.8 points per game. The Colts had 17 points by early in the second quarter.

The Titans hadn't given up a touchdown to a tight end all season. That's fine. Luck didn't try to force the ball to any of his tight ends, who have a league-high 15 touchdown receptions. He took advantage of the Titans' trying to single-cover receiver T.Y. Hilton with cornerback Adoree Jackson. Hilton had nine catches for 155 yards and two touchdowns.

Focus on trying to take something away and Reich and offensive coordinator Nick Sirianni will simply look to exploit the defense in another area. That's how multidimensional the Colts are on offense.

"I did visualize our offense being this way," tight end Eric Ebron said. "It's really getting everybody to buy in and then this offense would do exactly what it needs to do. ... [Defenses] have to pick a player. They picked me, and T.Y. went off. Andrew makes it easier for everyone. By that, we all are on the same page. We know what he's thinking, we're not out there guessing."

About the only thing that didn't go right for Luck and the Colts on Sunday was that they couldn't pull off the "Philly Special." Ebron's throw to Luck in the end zone was just out of reach of the quarterback's sprawling hands in the second quarter.

"I gave it my best effort, and I'll retire as a wide receiver from here on out," Luck said, laughing.

That's OK because Andrew Luck the quarterback is doing just fine for one of the NFL's hottest teams.