Andy Murray on mend as he practises with Scots teenager

Andy Murray is on the mend after hip surgery. Picture: John Devlin

The three-time grand slam champion has not played competitively since exiting Wimbledon at the quarter-final stage last July, and he has since lost his British No 1 ranking to Kyle Edmund.

However, Murray underwent surgery earlier this year and said he was targeting the beginning of the grass-court season in June to make his comeback. However, he could return sooner and it is understood that two new Challenger tournaments – one at the Scotstoun Tennis Centre in Glasgow starting on 28 April and the other at Loughborough University the following month – are on his radar.

On Wednesday he posted an image from his latest training session, with Scottish teenager Aidan McHugh.

Writing on Instagram, Murray wrote: “Chasing down another @aidymchugh error today during practice #progress #hip #unforced #youngpup”

McHugh, 17, from Glasgow, played at junior Wimbledon last year and has been mentored by Murray and his brother Jamie.

Meanwhile, American John Isner upset second-seeded Marin Cilic of Croatia 7-6 (0), 6-3 to reach the Miami Open quarter-finals. The 14th-seeded Isner, who reached the Miami Open semifinals in 2015, never faced a break point in the match. He made an impressive 73 percent of his first serves to take down Cilic.

The departure of Cilic, the 2014 US Open champion and Australian Open finalist in January, leaves fourth-seeded Alexander Zverev of Germany as the highest seed remaining in the draw.

Top-seeded Roger Federer lost his opening match at the tournament, and third-seeded Grigor Dimitrov of Bulgaria lost in the third round.

Fifth-seeded Juan Martin del Potro, a definite crowd favorite in Latin-influenced South Florida, moved onto the quarterfinals with a 6-4, 6-2 win over 22nd-seeded Filip Krajinovic of Serbia. Del Potro will play 20th-seeded Milos Raonic for a semifinal berth. Roanic defeated Frenchman Jeremy Chardy 6-3, 6-4. Isner will play 19th-seeded Hyeon Chung of Korea in the quarterfinals. Chung defeated Joao Sousa of Portugal, 6-4, 6-3.

No 6 seed Jelena Ostapenko is through to the semi-finals of the women’s tournament in Miami. Ostapenko ousted fourth-seeded Elina Svitolina 7-6, 7-6 to reach the semi-finals at Key Biscayne for the first time. Next up for Ostapenko is either No 8 seed Venus Williams or qualifier Danielle Collins in the semi-finals.