Top seeded Roger Federer rallied from a set down to defeat Denis Istomin 3-6 6-3 6-4 and meet Bulgarian star Grigor Dimitrov at the quarterfinals of the Swiss Indoors in Basel on Thursday.

The Shanghai Open winner was stretched to the limits, compared to his 47 minute match in the opening rounds, by Istomin of Uzbekistan who was ruthless in the first set as Istomin fired off four service aces and broke the Swiss once to take charge of the first set.

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The 17-time Grand Slam champion bounced back in the second set as he delivered all of his first serves and jumped at every second return point opportunities he gets to break the 28-year-old Istomin once and level the match at 1-all.

In the third and deciding set, the Swiss only needs one break point to seal the match as he converted his last attempt out of eight to win Federer's sixth match against Istomin and advance to the quarterfinals in an hour and 48 minutes.

"I thought I was lacking rhythm in the first set," Federer said. "It was one of those sets that was tough to lose but the important thing was to bounce back in the second set and get my teeth into the match."

Federer, who is looking to claim his sixth title of the tournament, will meet fifth seeded Dimitrov in the quarterfinals who had an easier second round matchup against Canadian Vasek Pospisil.

The If Stockholm Open finalist was relentless in his match against Pospisil as he didn't give the Canadian a chance to break Dimitrov and kept the pressure in both sets to force Pospisil to hit errors that eventually led to his demise.

Dimitrov, 23, broke Pospisil twice in both sets to win it 6-2 6-2 in a match that lasted an hour and four minutes.

In other matches, hard-hitting eighth seed Ivo Karlovic also made it into the quarters after he defeated Kenny de Schepper in a hard earned three setter 6(6)-7(8) 6-4 6-3.

The Croatian is set to meet Benjamin Becker of Germany who won against Mikhail Kukushkin who retired after being down 4-0 in the third set.

TagsRoger Federer, Grigor Dimitrov, Ivo Karlovic