LAS VEGAS — It’s been 18 months since Brian Bowles stepped into the cage. The former WEC bantamweight champion had lost little standing in the meantime, and had entered the fight No. 8 in the UFC’s rankings. After Saturday night, he may disappear from the top 10.Bowles got off to a decent start in his UFC 160 matchup with George Roop, but seemed to run out of gas after the first round. Roop eventually floored him with a left jab, and then finished him with ground strikes for an upset TKO.The finish came at 1:43 of the second round.Bowles did a decent job in overcoming Roop’s length advantage in the first, and at one point late in the round, got inside far enough to drop Roop with a right cross behind the ear. He followed on the ground hunting for a guillotine submission, but Roop survived the attempt. Bowles had full mount to end the round, but couldn’t finish.As it turned out, that was his last chance, as Roop changed things up in the second, and Bowles faded.Roop won his second straight since returning to bantamweight, and is now 13-10-1. It was also his second win in two months, as he also won in March. Bowles, who hadn’t fought since a submission loss to Urijah Faber at UFC 139, is now 10-3.