Andy Murray made a winning start to his ATP grass-court season after a straight-sets victory over Christopher O'Connell at the Stuttgart Open.

The three-time Grand Slam champion, who reached the Surbiton Open semi-finals last week, recovered from a slow start before wrapping up a commanding 6-4 6-3 victory in Stuttgart.

Having missed the French Open to focus his efforts on Wimbledon, Murray lost the opening three games of his clash with the Australian qualifier.

However, the former world number one responded in style, breaking his opponent four times on the way to setting up a last-16 clash with Alexander Bublik.

Bublik, the seventh seed, hit 19 aces and won 36 out of 42 points on his first serve as he overcame Denis Kudla 7-6 (7-3) 7-5.

Nick Kyrgios recorded an impressive 18 aces in his 7-6 (7-3) 6-3 win over Jiri Lehecka, but eighth seed Ugo Humbert was ousted 4-6 7-6 (7-4) 6-4 by compatriot Arthur Rinderknech.

Meanwhile, Botic van de Zandschulp and Tommy Paul were among the seeds to fall at the Rosmalen Grass Court Championships.

Sixth seed Van de Zandschulp went down 4-6 6-2 6-1 against Finland’s Emil Ruusuvuori, and seventh seed Paul was beaten 6-7 (7-4) 7-6 (7-5) 7-6 (7-2) by American compatriot Brandon Nakashima.

But there were no such problems for Karen Khachanov. The world number 23 won 28 out of 30 points on his first serve as he downed Alejandro Tabilo 6-3 6-3.