Grigor Dimitrov has progressed at the Madrid Open after Donald Young was forced to retire during their first-round match.
World number 11 Dimitrov was leading 6-4 3-0 before a back problem made it impossible for Young to continue.
The Bulgarian will now face Italy's Fabio Fognini for a berth in round three.
Dimitrov reached the third round of last year's tournament before losing to Tomas Berdych.
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