Mike Groll/AP/Press Association Images Federer will now face either Tomad Berdych or Nicolas Almagro.
# Walkover
Federer into US Open last eight as Fish pulls out
Elsewhere, Ana Ivanovic today ended a four-year wait to reach the quarter-finals of the competition.

Updated at 18.43pm

WORLD NUMBER ONE Roger Federer received a walkover into the US Open quarter-finals Monday when America’s Mardy Fish withdrew from their last-16 tie due to “health reasons”, an event spokesman said.

Five-time champion Federer will face either Czech sixth seed Tomad Berdych or Spanish 11th seed Nicolas Almagro for a place in the semi-finals.

It will be the top seed’s 38th Grand Slam quarter-final.

“Mardy Fish has withdrawn for health reasons,” said the spokesman.

Fish, 30, missed two months of the season earlier this year because of a heart problem.

He was hospitalised after the Miami Masters in March when his heart rate increased to three times its normal resting rate.

The American then underwent a procedure called a cardiac catheter ablation in Los Angeles on May 23 to correct faulty wiring in his heart.

Meanwhile, Serb 12th seed Ana Ivanovic reached her first Grand Slam quarter-final in four years, and first ever at the US Open, when she defeated Bulgaria’s Tsvetana Pironkova 6-0, 6-4 on Monday.

The 24-year-old, whose last major quarter-final came on the way to her one and only Grand Slam triumph at the 2008 French Open, swept through the first set in just 23 minutes, firing 13 winners and giving up just 11 points.

Pironkova, the world number 55 who became the first Bulgarian to make a Grand Slam semi-final when she charged into the last four at Wimbledon in 2010, was the first woman from her country to make the last 16 in New York since 1994.

But her challenge was restricted by a neck injury and she twice needed treatment, including a medical time-out at the end of the first set.

She battled gamely in the second set, breaking Ivanovic twice, including the ninth game when the former world number one was serving for the match.

But the Serb hit back immediately for victory in the 10th game with the match’s 10th break of serve in the 16 games played.

“I hardly made any mistakes in the first set but she is a tough opponent and I knew she would come back in the second set,” said Ivanovic after her 71-minute win, where she finished with 28 winners and 21 unforced errors.

“It’s amazing to be in my first quarter-final at the US Open.”

Ivanovic will next face either three-time champion Serena Williams, who is targeting a 34th career Grand Slam quarter-final spot, or Czech world number 82 Andrea Hlavackova.

- © AFP, 2012

Read: Injured Nadal to miss at least next 2 months>

Read: From dawn till dusk: Roddick stays alive on late night in New York>