UFC middleweight champion Robert Whittaker will defend his title later this year against top contender Kelvin Gastelum, the UFC announced Friday night.

Multiple sources told ESPN's Ariel Helwani the targeted time frame for the matchup would be the end of 2018. Both fighters also will coach the next season of "The Ultimate Fighter" reality television series.

Robert Whittaker defeated Yoel Romero by decision on Saturday at UFC 225 to retain the middleweight belt. Andrew Hancock for ESPN

Whittaker (20-4) is coming off a split-decision victory over Yoel Romero last month at UFC 225. Following the fight, Whittaker had surgery on his broken right hand, and, according to sources, the surgery was a success. The promotion did not announce a date for the fight because it wants to see how Whittaker's hand heals.

Gastelum (15-3, 1 NC) has won his past two fights. He most recently defeated Ronaldo Souza in May via split decision.

The race to fight Whittaker next came down to Gastelum and former 185-pound champion Chris Weidman, who beat Gastelum last July. Weidman is expected to return in the fourth quarter of 2018.