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Shelton defeated another compatriot, Ethan Quinn, 6-4 5-7 6-4 in two hours and 18 minutes to set up a last-eight clash against Fritz, who he beat in the Stuttgart final.

After squandering two break-point opportunities in the very first game against Quinn, Shelton broke ahead in the ninth game before securing the first set a game later.

Quinn, however, was determined to stay in the match, saving five break points in the 11th game of the second before converting one of his own at the third time of asking to force a decider.

Third seed Shelton found himself 2-0 down to start the third, but his quality then came to the fore as back-to-back breaks gave him control of the last-16 tie once again.

The 23 year-old got over the line with his first match point, continuing his momentum before Wimbledon starts later this month.