Kelly, listed at 6-foot-8 and 321 pounds, became the heaviest player in league history to catch a touchdown in the postseason with his 1-yard score at the 6:43 mark in the second frame. The touchdown gave the Titans a 17-7 lead over the Chiefs in the AFC title game.
Titans offensive coordinator Arthur Smith fooled the Chiefs into thinking star running back Derrick Henry, who was lined up at fullback, was going to get the ball in a short-yardage situation. Instead, veteran quarterback Ryan Tannehill faked the handoff and lobbed the ball to Kelly for the easy touchdown.
It marked Kelly's second receiving touchdown of the season. He also scored on a similar play-action pass against the Jacksonville Jaguars on Nov. 24.
Kelly became the first offensive lineman since 2000 with two receiving touchdowns in a single season, according to NFL Research. He is the third player to weigh 300-plus pounds over that span to accomplish the feat.
The Chiefs held a 21-17 lead over the Titans at halftime.