On the heels of Robbie Lawler's first UFC welterweight title defense, longtime boxing coach Matt Pena has resigned from the fighter's camp.

Pena, who lives in Salt Lake City, has worked with Lawler since 2005. The two met at Miletich Fighting System in Bettendorf, Iowa, where Pena was a member of former UFC welterweight champion Matt Hughes' camp.

Since 2012, Lawler (26-10) has trained at American Top Team in Coconut Creek, Florida, where Pena has flown in for each fight camp. Pena was in Las Vegas for Lawler's thrilling TKO win over Rory MacDonald at UFC 189 on Saturday, and the coach says that will be his final fight with Lawler.

"It is with deep regret that I'm resigning as boxing coach for Robbie Lawler, ending over 10 years of dedication to the UFC welterweight champion," Pena said. "I have received tremendous satisfaction knowing that I am one of the few that told people years ago that he was the best welterweight in the world.

"There are really only two things left that I've wanted to help accomplish in the sport of MMA. One was watching Robbie enter the Hall of Fame, which I'm sure he will at the end of his reign. The only other thing I wanted to do was help him get a win over Georges St-Pierre, who I'm sure will never come back after what he saw on Saturday. So it's safe to say I've done all I can do in this sport as a boxing coach."

Lawler, 33, is 7-1 since returning to the UFC in early 2013. He made his debut in the promotion in May 2002 as a 20-year-old. He fought outside the promotion from 2005 to 2012, primarily as a middleweight.

Pena, who will continue to coach boxing outside of MMA, didn't rule out a return to the cage, but said, "I don't see it at the moment."

"I would like to thank Pat Miletich, Matt Hughes, Jens Pulver, Tim Sylvia and Spencer Fisher for giving me an opportunity of proving the effectiveness of my grandfather Alvino Pena's boxing style in the sport of MMA. I've helped three men get UFC championships and was privileged to work with a couple of other champions during their career. I know that I've been fortunate enough to work with legends, a small group of athletes in Iowa who became the best in the world.

"My reasons for stepping away I will keep private right now. The only folks that I feel are entitled to that information are me and Robbie."