Brown had 11 receptions for 145 yards and a touchdown in his first game back from injured reserve. He was itching to get back onto the field as he went through the rehab process.
"I'm very grateful just to play football again," Brown said. "I missed playing football. It was tough for me because this is what I love to do. I really feel like this is my purpose of living."
Brown came up big for quarterback Ryan Tannehill, especially on third downs. The third-year receiver had eight receptions on third downs for the Titans. That's the most by any player in a game over the past 30 seasons, according to ESPN Stats & Information research.
"I love throwing the ball to A.J. [Brown]," Tannehill said. "He has a natural ability to get himself open. He has his size and his strength. There are some guys that they are just easy to throw to. He is one of those guys."
Added Brown, "Third down, that's the money down. You gotta convert it and keep these drives going."
Brown accounted for 69.4% of the Titans' receiving yards, the highest percentage by any player this season whose team threw for at least 200 yards. Brown has accounted for three of the five highest percentages since last season, according to research by ESPN Stats & Information.
Tennessee had failed to score any points since the second quarter of Sunday's game against the Pittsburgh Steelers before Brown's two third-down receptions on the opening drive of the third quarter led to a field goal. The Titans outscored the 49ers 20-7 in the second half to secure the win.
"A.J. was bringing the juice to us on the sideline," Titans safety Kevin Byard said. "He was out there working those boys. You obviously see how much he means to our team, our offense. He's a guy that brings that energy."
The Titans, who had lost three of four games heading into Thursday and had two starting offensive lineman ruled out this week, can capture their second consecutive AFC South division title if the Indianapolis Colts lose to the Arizona Cardinals on Saturday.
"The funeral for the Titans was supposed to be yesterday or today," coach Mike Vrabel said. "We're not dead yet."
QB breakdown: Tannehill had a tough first half, during which the Titans gained just 55 total yards on offense. But he rebounded in the second half, and overall he completed 22 of 29 passes for 209 yards and a touchdown. It was the first time he threw for more than 200 yards in the past five games.
Tannehill connected with Brown for an 18-yard touchdown in the third quarter. It was Tannehill's first passing touchdown since Week 12 against the Patriots and snapped a streak of 102 straight pass attempts without a passing touchdown. There seemed to be a different level of confidence from Tannehill with Brown back in the lineup. He made a couple of tight-window throws and gave his receiver a chance to make plays down the field.
Breakout performance: Brown had his best game of the season, topping his 10-reception, 155-yard performance against the Colts in Week 7. Brown now leads the Titans in receptions (56), yards (760) and receiving touchdowns (four).
Pivotal play: Down by a touchdown in the third quarter, Titans safety Amani Hooker stepped in front of a Jimmy Garoppolo pass that was intended for Deebo Samuel. Hooker returned the interception to the 49ers' 18-yard line. The Titans punched it in for the game-tying score four plays later.