INDIANAPOLIS —When the Texans made moves for Joe Mixon and Stefon Diggs in consecutive months this offseason, some questioned those moves.

Mixon was almost 29, the Bengals had just released him and many wondered if he could still do it.

Meanwhile, Diggs was 30 and the Bills were eager to trade him after his production dipped in the second half of last season.

But in the Texans’ 29-27 season-opening win over the Colts at Lucas Oil Stadium on Sunday, it was both Mixon and Diggs who showed why the Texans wanted to pursue the two stars.

TEXANS 29, COLTS 27: How the game went.

They accounted for all three of the Texans’ touchdowns, including Diggs’ fourth-quarter score that gave Houston a two-possession lead late in the game.

Diggs, who caught all six of his targets for 33 yards, finished with two receiving touchdowns. And Mixon had a rushing touchdown to go along with his 159 yards rushing.

“Those guys can step up and make plays no matter what the situation is,” coach DeMeco Ryans said, his voice still hoarse from yelling during the game. “And when you can count on those guys to make plays, that’s a huge deal for our team.

“Not just the attack.”

REPORT CARD: The Texans Rate

The Texans needed that in a thrilling game that was decided only in the final two minutes.

They made two of the game’s three key plays in the fourth quarter, with the game on the line.

The Texans faced a fourth-and-goal from the Indianapolis 2-yard line with a 22-20 lead with just under five minutes left.

The Texans ran a play specifically for Diggs, who ran an out route to the left corner of the end zone. Stroud threw a perfect pass to Diggs for his second touchdown of the day.

After the Colts cut the lead to 29-27 on their next possession, the Texans faced another critical situation three minutes later on third-and-3 with 1:48 left. They threw the ball to Mixon, who dodged a pair of defenders en route to a gain of 9 yards and a first down to secure the victory.

The Colts ran out of timeouts.

“It was supposed to go frontside, and basically the linebacker screened over the top and I replaced his gap where he was supposed to go, and I made him pay for it,” Mixon said of the play. “I’m just glad I was able to close it out at a crucial time.”

On a day when the Colts made things difficult for Stroud by throwing multiple passes and limiting deep passes, Mixon was steady and consistent.

He didn’t hesitate for a moment and averaged 5.3 yards per attempt.

“He was huge,” Stroud said of Mixon. “If you can impose your will by running the ball, you can open up a lot of types of plays that Bobby (Slowik) can call. Honestly, we just kept doing it and I think it worked.”

The Texans had more explosive run plays than explosive pass plays.

The Texans’ only explosive passing play — a 55-yard pass from Stroud to Nico Collins — came on a play-action pass. When Stroud faked the run, he caused some Colts defenders to hesitate, allowing Collins to get behind the defense.

Stroud was solid Sunday, finishing 24 of 32 passes for 234 yards and two touchdowns.

But it was Mixon who controlled the match.

One of the biggest questions heading into the matchup was how Mixon would look on offense. He missed a couple of weeks with a quadriceps injury early in training camp, but returned to the field in the final two weeks.

He didn’t miss a beat, though. Despite the Colts having one of the best front sevens in the NFL, Mixon couldn’t and wouldn’t be stopped.

It didn’t matter whether he faced a packed penalty area (eight or more defenders), a neutral penalty area (seven in the penalty area) or a light penalty area, he was successful against everything the Colts threw at him.

According to the NFL’s Next Gen Stats, four of his 30 runs went for 10 yards or more.

“You have to give the O-Line credit,” Diggs said, adding that Mixon probably could have gotten more. “We get all the hype and celebrations and stuff, but the game is won up front. Our O-Line dropped their n—- when they had to. Came up with a dub. It’s a game-changer when you can run the ball with two minutes left.”

The Texans had three 100-yard rushers last season (19 games), including the playoffs. Mixon ran for 104 yards in the second half alone. His 159 yards rushing were the third-most of his career. He also added three catches for 19 yards.

The Texans dominated the possession battle, 40 minutes versus the Colts’ 20. That’s something they couldn’t do last season with Dameon Pierce and Devin Singletary as lead backs.

“Joe hit those holes,” left tackle Laremy Tunsil told the Chronicle. “He was determined to get a first down and get positive yards. I think it’s just his mindset. I don’t want to talk bad about anybody else, but Joe’s just a little bit different. Joe’s hungry. Joe wants it.”

Credit the offensive line as well. Mixon had holes to run through. But he also added a little spice with his physicality as he ran over defenders constantly.

Tunsil said Mixon told the offensive line all week that he wanted 100-plus yards, and he delivered on that promise.

“He puts in the work, he puts in the training and then he shows he can do it,” Tunsil said.

The Texans traded a seventh-round pick for Mixon a day after the free agency period opened and just hours before the Bengals planned to release him.

Houston needed a running back and found one in Mixon, who had developed into one of the best running backs in the NFL during his time in Cincinnati.

The following month, the Texans traded a future second-round pick for Diggs, a four-time Pro Bowl receiver who was also considered one of the best route runners in the NFL.

It was a clear sign that the Texans were trying to compete for the Super Bowl while Stroud was still under his rookie contract. They weren’t going to wait.

Both have proven their worth so far.

The Texans are off to a 1-0 start to the season after taking a win in the final game of last year over a Colts team that was in contention for the AFC South title.

They will probably continue to compete with them until the end of this year.

But it helps having Diggs and Mixon there.

That’s why the Texans acquired both of them.

“Extremely strong football players, they love the game and they play the game the right way,” Ryans said. “It jumps off the tape and they’re great people. Adding those guys to our team, obviously Stef being the captain and Joe being on the leadership council as well, those guys are leaders as well.

“It’s just very valuable.”