A step down in weight class didn’t change anything for B.J. Penn.

The former two-division world champion likely stepped inside the cage for the final time on Sunday night before weathering a brutal third-round TKO loss to Frankie Edgar in the main event of the "Ultimate Fighter 19 Finale" show at the Mandalay Bay Events Center in Las Vegas.

Edgar (16-4-1) beat Penn (16-10-2) for the third time in his career, stopping him at 4:16 of the third round after a vicious ground and pound left Penn bloodied in the middle of the cage.

Once it was over, the 35-year-old Penn said he made a mistake returning after an 18-month layoff.

"I shouldn’t have come back," Penn said in a postfight interview with commentator Jon Anik. "I shouldn’t have been in the ring tonight. (UFC president) Dana (White) said it was over and I’ve got to agree with him at this point."

Penn’s first fight at 145 pounds looked similar to his last two fights at 170 pounds.

Edgar, who is the only fighter in the past nine years to beat Penn at a weight less than 170, controlled the entire fight from the opening bell.

Penn came out standing upright and offered little offense on his feet as Edgar weaved in and out, pelting Penn’s face with lightning-quick punches.

Once Edgar decided to take Penn to the mat, the Hilo native offered little resistance, seemingly inviting Edgar to take position on top.

Edgar turned it up toward the end of the second round and finished it on the ground in the third. An elbow opened up a gash above Penn’s left eye and Edgar finished it a minute later with an onslaught of strikes that Penn couldn’t defend.

Penn, whose first fight in the UFC came in 2011, successfully defended the UFC lightweight title three times after beating Joe Stevenson in January 2008.

Edgar ended his reign in 2010 by handing Penn one of five losses in his last seven fights.