Jayne Kamin-Oncea-USA TODAY Spor

After 45 professional fights, with nine of them taking place in the UFC, veteran lightweight Aaron Riley retired from the sport on Saturday night.

Riley competed at the UFC on Fox 8 show where he lost a split decision to Justin Salas. Following the bout, Riley took to Twitter to announce that his fight in Seattle was the last of his 16-year career.

Riley began fighting all the way back in 1997, competing in the HooknShoot promotion for the first seven fights of his career.

Even in those early days, Riley already had built a reputation for being one of the toughest fighters in the sport who was willing to step up and face anybody inside the cage or ring.

After more than 20 fights in the local circuit, Riley finally got his shot at the UFC in May 2002, where he lost a hard-fought unanimous decision to Robbie Lawler at UFC 37.

Following the loss, Riley went back to competing in regional promotions before earning a chance to compete in Pride Fighting Championships in 2005, where he knocked out Michihiro Omigawa with a stunning first-round head kick.

That fight earned Riley a shot back in the Octagon, but his fight against Spencer Fisher ended after only one round. Not because Riley got knocked out or submitted, but because he suffered a broken jaw during the fight.

Riley exited the UFC once again after that loss, but returned in November 2008 and never fought for another promotion again.

Riley closed out his career with a 3-4 record in the UFC, picking up wins over notable names like former Ultimate Fighter competitor Jorge Gurgel and Shane Nelson.

In an unfortunate twist, Riley actually suffered a second broken jaw during his return to the UFC in his fight against Tony Ferguson in 2011.

The injury and subsequent time off put Riley on the sidelines for over a year until he finally returned to action on Saturday night at UFC on Fox 8.

Riley fought valiantly and put on a show for the fans as he was always known to do throughout his career.

While he was never a top champion or even a contender for the biggest part of his 16 years in the sport, Riley will always be remembered as a respected veteran who might have been one of the toughest fighters ever to lace up his gloves and step into an MMA arena.

Damon Martin is a Featured Columnist for Bleacher Report