LOS ANGELES: Colombian Alejandro Falla produced the first upset at the LA Open with a gripping and occasionally tempestuous 4-6 6-3 7-6 victory over fifth-seeded Latvian Ernests Gulbis in the second round on Thursday.

The Colombian will take on top seed Andy Murray in the quarter-finals, the Briton surviving a second-set wobble and a stiff back to beat American qualifier Tim Smyczek 6-1 4-6 6-2.

World number four Murray, playing his first tournament since his semi-final loss to Spaniard Rafa Nadal at Wimbledon earlier this month, broke the unheralded Smyczek three times in the final set to advance on a cool evening.

Left-hander Falla came from 0-3 down in the third set and needed five match points before clinching the tiebreak 10-8 against a temperamental Gulbis at the LA Tennis Center.

Gulbis, who was repeatedly warned by the umpire for racket abuse, appeared to have the match firmly within his grasp after taking early control in the third set but he then lost three successive games for Falla to level.

Although the Colombian failed to serve out when leading 5-4 and squandered a 6-4 advantage in the tiebreak, he finally wrapped up victory in two hours and 15 minutes when Gulbis netted a backhand.

"I played really well in the last set," a beaming but exhausted Falla said courtside after reaching his second ATP quarter-final of the year. "We were both tired ... and I am really happy to get through."