CINCINNATI, July 31, 2008 (AFP) - Former tennis camp companions Novak Djokovic and Ernests Gulbis set up their second battle in as many months by reaching the quarter-finals of the ATP Cincinnati Masters on Thursday.

Third seed Djokovic, riding his best run of form in the steamy American Midwest, swamped his second straight Italian opponent as he crushed Andreas Seppi 6-1, 6-2 a day after beating Simone Bolelli in two tie-breakers.

Serbian Djokovic, 21, and Latvian teenager Gulbis hung out as kids when they attended the tennis academy of Niki Pilic in Munich, with Djokovic always refraining at elaborating on any of their off-court adventures.

Gulbis reproduced his French Open form over luckless James Blake, sending the veteran US seventh seed down to a 6-4, 1-6, 6-3 upset.

'I haven't played against top 10 players so much in my career, so beating one of them gives me more confidence,' said the world number 53, who still seeks his first career ATP final.

'I knew that he's a tougher opponent on hard court than he is on clay, so I was a little bit nervous, but as the match went on I played pretty well in the beginning, though I lost my concentration in the second set.'

Djokovic, who won the Australian Open and a pair of spring ATP Masters Series titles, has gone off the boil in recent months as Rafael Nadal and Roger Federer lift the tight rankings race for number one to a new level.

Spaniard Nadal, winner of seven titles his season, trails the Swiss by 300 points, his narrowest margin in years.

Swiss Federer is fighting to retain in Cincinnati title and put some traction into his season with the Beijing Games his next date on court.

Djokovic owns a flawless 4-0 record over Seppi, whom he also beat in California in March. The Serb fired eight aces and broke five times to dominate in 59 minutes.

Spain's Carlos Moya finished off a match interrupted in the second set by rain overnight, putting out Russian fourth seed Nikolay Davydenko 7-6 (10/8), 4-6, 6-2.