The Tennessee Titans clawed their way back from being 10 points down at half-time to beat the San Francisco 49ers 20-17 with just seconds remaining.

Quarterback Ryan Tannehill had just 40 yards through the air for the first half but upped his game after the break to finish with 209 yards and a touchdown.

Tannehill led his side on a 55-yard, 13-play drive at the start of the third quarter which ended with kicker Randy Bullock slotting a 38-yard field goal which marked the Titans' first points.

Following a turnover, Bullock converted running-back D'Onta Foreman's three-yard touchdown run to bring the score level at 10-10.

Wide-receiver AJ Brown latched on to a Tannehill pass just after the start of the fourth to take his side ahead for the first time, before 49ers quarterback Jimmy Garoppolo connected with Brandon Aiyuk to make it 17-17 with two minutes left.

Enter Bullock, who calmly nailed a 44-yard field goal with four seconds remaining to ensure the victory.

The Titans are one win away from securing their second-straight AFC South title, and can achieve it early if the Indianapolis Colts lose to the Arizona Cardinals on Christmas Day.