Juan Martin del Potro is through to the semi-finals of the Delray Beach Open in Florida – his first tournament since March 2015.

The 2009 US Open champion, who is making a comeback from a third round of surgery on a troublesome wrist injury, beat France’s Jeremy Chardy 6-4 6-3 in just over an hour.

That sets up a last-four encounter with Sam Querrey, who won the all-American quarter-final with qualifier Tim Smyczek 6-7 7-6 6-4.

Fourth-seed Grigor Dimitrov is also into the last four after beating Adrian Mannarino in straight sets. The Bulgarian needed an hour and 20 minutes to win 6-4 7-5.

He will now face Rajeev Ram after the American got the better of Benjamin Becker in three sets, winning 3-6 6-4 6-3.