Andy Murray was outplayed by Russia’s Daniil Medvedev as he lost 7-5 6-2 in the second round of the Brisbane International.
Medvedev, the world number 16, looked strong against the Briton in his first tournament since September.
The 22-year-old was solid and Murray failed to cope with his power.
Murray is a three-time Grand Slam winner but is currently ranked 240 in the world after only playing six tournaments in 2018.
After his opening round win over Australian wildcard James Duckworth, the 31-year-old admitted he did not know how much longer he would be able to play top-level tennis after hip surgery.
Earlier, British number one Kyle Edmund suffered a shock defeat by Japan’s world number 185 Yasutaka Uchiyama.
Edmund, the world number 14 and third seed, lost 7-6 (8-6) 6-4 to the qualifier.