The San Francisco 49ers, led by two-time Pro Bowl defensive end Nick Bosa, turned in a mighty defensive performance against Tennessee on first and second down.

Third down was another story.

The Niners gave up big play after big play on Thursday night with a chance to get off the field and blew a 10-0 halftime lead in losing 20-17 to the Tennessee Titans.

"It was tough, especially towards the end," Bosa said.

"Those are the plays that we need and if you don't make them, it's definitely deflating."

The 49ers looked dominant on first and second downs, holding the Titans to an average of 3.19 yards per play. On third down, the Titans averaged nine yards per play.

The loss was only the second in seven games for the Niners (8-7) who snapped a two-game winning streak. Their loss clinched a playoff berth for Dallas (10-4) and trimmed San Francisco's margin for error with two to play.

The 49ers (8-7) still sit in the No.6 seed in the NFC as the second wild-card with Minnesota (7-7) right behind - though San Francisco have the head-to-head tiebreaker thanks to a 34-26 win over the Vikings last month.

Titans quarterback Ryan Tannehill threw for just 40 yards in the first half but finished with 209 yards and a touchdown. A.J. Brown caught 11 passes for 145 yards, and his 18-yard TD catch gave the hosts a 17-10 lead early in the fourth.

"It was all on us and we just had to make a play," Brown said.

"Then we had to make another play. That was the mindset. Just come out here and make plays, so that's what we did."

San Francisco QB Jimmy Garoppolo threw for 322 yards, converting 26 of 35 attempts for one TD to Jeff Wilson, but was intercepted twice.

"It's tough when you let one like this slip away," Garoppolo said.