HOUSTON — In the span of four weeks, Houston Texans quarterback Ryan Fitzpatrick underwent the transformation from displaced starter to dynamic replacement and delivered a performance as surprising as it was timely.

Fitzpatrick passed for 358 yards and a career-best six touchdowns in his return to the starting lineup to lead the Houston Texans to a 45-21 victory over the Tennessee Titans on Sunday at NRG Stadium.

Fitzpatrick, benched following a loss to the Philadelphia Eagles on Nov. 2, completed 24 of 33 attempts and posted a 147.5 passer rating substituting for Ryan Mallett, who was lost to a season-ending pectoral injury. Fitzpatrick tossed a pair of scoring passes to wide receiver DeAndre Hopkins, whose 238 receiving yards represented a career best.

“Like I said when we made Mallett the starter, it wasn’t all Fitzy’s fault,” Texans coach Bill O’Brien said. “We just felt like we were making a decision that was best for the team at the time.

“Like I said this week, maybe it helped Fitz to take a step back. Maybe that (the benching) helped Fitz to see how the offense was operated. He went in there and did a good job.”

Texans defensive end J.J. Watt also got in on the act, catching a 1-yard touchdown pass from Fitzpatrick after his sack of quarterback Jake Locker resulted in a fumble. Watt recovered that fumble and his short return delivered Houston (6-6) possession at the Titans 24-yard line.

Watt has accounted for five touchdowns this season, three on offense.

Tennessee (2-10) dropped its sixth consecutive game. After surrendering 212 rushing yards to the Texans in the first meeting between the AFC South rivals on Oct. 26, the Titans allowed just 99 rushing yards on Sunday. But their inability to mount a pass rush against Fitzpatrick enabled him to pick apart the Titans secondary.

The Texans secured a 14-0 lead with haste, covering 80 yards on 14 plays on an opening drive capped by an 8-yard Fitzpatrick touchdown pass to tight end Ryan Griffin.

Texans cornerback Johnathan Joseph followed with an interception of Titans starting quarterback Zach Mettenberger, a turnover that returned possession to the Texans at the Tennessee 20.

Four plays later, Fitzpatrick hit running back Arian Foster for a 7-yard scoring toss. Just prior to the intermission, Fitzpatrick and Hopkins completed the first of their two scoring connections, with Hopkins hauling in a 58-yard strike with 38 seconds left for a 24-0 lead.

What the Texans said:

“It was an unreal throw by Fitz (Texans quarterback Ryan Fitzpatrick). He put it in a spot where nobody but me could get it and it was a perfect throw. He really couldn’t have put it in a better spot. It was just a matter of going out there and grabbing it. All of the credit goes to him on that.” — Texans defensive end J.J. Watt on his 1-yard touchdown catch in the fourth quarter, his fifth touchdown on the season.

What the Titans said:

“It could have just been football, but considering I was the target that Met (Titans quarterback Zach Mettenberger) was throwing to on the screen, I definitely think it was a late hit. The ball was already gone. I guess why hit him anyway?” — Titans wide receiver Kendall Wright on the hit by Texans defensive end J.J. Watt that knocked Mettenberger from the game.

What we learned about the Texans:

1. DeAndre Hopkins has surpassed Andre Johnson as the Texans’ No. 1 receiver. One could argue that Hopkins wrestled this title from Johnson earlier this season, but Hopkins’ breakout performance against the Titans cemented the anointing. Hopkins set career highs in receptions (nine) and receiving yards (238) while grabbing a pair of touchdowns. Johnson still leads the teams with 65 catches, but Hopkins paces the Texans with 1,041 receiving yards and six touchdown catches.

2. As improbable as it may seem, defensive end J.J. Watt has built a solid case as league MVP. Watt finished with three tackles, two sacks, six quarterback hits, a forced fumble and a fumble recovery on defense. He added a 1-yard touchdown catch in the fourth quarter for his fifth touchdown this season, his third on offense. “It’s what you dream about,” Watt said after being bathed by MVP chants in the fourth quarter.

–QB Ryan Fitzpatrick set a franchise record with six touchdown passes and became the fifth quarterback in Texans history to record a 300-yard passing game. Fitzpatrick finished 24 of 33 for 358 yards and recorded scoring strikes to TE Ryan Griffin, RR Arian Foster, WR DeAndre Hopkins (twice), WR Andre Johnson and DE J.J. Watt. Fitzpatrick is the eighth quarterback to record a four-touchdown game with three different franchises (Buffalo and Tennessee).

–DE J.J. Watt recorded his third receiving touchdown on the season, a 1-yard reception from QB Ryan Fitzpatrick. Watt also has an interception return for a score and a fumble return for a touchdown. He notched two sacks on Sunday, bumping his team-leading total to 11.5.

–WR DeAndre Hopkins set new career marks for receptions (nine), receiving yards (238) and touchdowns (two). Hopkins had seven catches for 117 yards and a touchdown against Tennessee in the second game of his rookie season last year and in four career games against the Titans, Hopkins has 25 receptions for 485 yards and three touchdowns.

What we learned about the Titans:

1. Baring a long-term injury to Zach Mettenberger, Jake Locker has likely started his last game for the Titans. Mettenberger was knocked from the game on Sunday with a right shoulder injury, opening the door for Locker to perhaps reopen the competition at quarterback. Instead, Locker tossed a pair of interceptions, was sacked twice and completed just half of his 12 attempts for 91 yards. “I’d like to have a few of them back, that’s for sure,” Locker said.

2. For all of their sporadic play on offense, the Titans remain a mess defensively. Tennessee surrendered 40-plus points for a second consecutive week and the third time this season, doing so against a quarterback (Ryan Fitzpatrick) that had been benched earlier this month and regained his starting job only due to injury. The Titans were ranked 28th in the NFL in total defense and allowed 457 yards to the Texans. “We can’t pack it in,” Titans linebacker Derrick Morgan said. “We can’t give up on the season as far as playing for something.”

–WR Justin Hunter was hospitalized with a lacerated spleen and remained in Houston overnight for observation. Hunter was injured on a blindside hit delivered by Texans FS Danieal Manning during a first-quarter interception by Texans CB Johnathan Joseph. Hunter actually returned to the game before being removed and hospitalized.

–QB Zach Mettenberger was sidelined with a grade-1 AC sprain in his right shoulder, an injury suffered on a hit delivered by Texans DE J.J. Watt. Mettenberger is scheduled for an MRI on Monday. Before departing, Mettenberger passed for 184 yards and a touchdown while also tossing an interception. He produced a 95.1 passer rating, his third such rating above 90 for the third time in six starts.

–WR Kendall Wright set a new career mark with his fifth touchdown on the season, a 36-yard reception from Titans QB Zach Mettenberger in the third quarter. Wright finished with seven receptions for 132 yards and became the second receiver in franchise history with at least 50 receptions in each of his first three seasons (Ernest Givins, 1986-88). Wright has 51 receptions for 633 yards this season.