Nick Krygios' troublesome hip has flared again during a straight-sets loss to fellow young gun Alexander Zverev at the Rogers Cup in Montreal.
The Australian was blown away 6-4 6-3 by the world No.8 on Thursday, losing the third-round clash in 72 minutes.
The 22-year-old Kyrgios was outplayed by the German despite winning their only two previous meetings, both this year.
Kyrgios was broken in third game of the first set before being unable to take six chances to break back.
He was less competitive in the second set, dropping serve twice including the last game to love to hand his fourth-seeded opponent a place in the quarter-finals.
Kyrgios, ranked 24 in the world, appeared to be battling soreness throughout the match and received treatment to the hip which forced his retirement from Wimbledon last month.
He faded in the second set, winning only 33 per cent of points on his second serve and being unable to take two break points in the penultimate game.
He could only save one of four break points for the match, with Zverev sending down 24 winners to 19.
"I'm happy to be through," Zverev said.
"Obviously against him, it's not easy because he's one of the biggest servers that we have.
"He plays with not a lot of rhythm."
Kyrgios was in near career-best form during his last meetings with 20-year-old Zverev, winning in Miami and Indian Wells this year.
But since the last clash in Miami in March, their paths have diverged as Kyrgios dropped from being the world No.16 at the time mainly due to injuries.
Zverev, meanwhile, is entrenched in the top 10 from 20th having reached the round of 16 at Wimbledon and claiming ATP titles in Rome and last week in Washington.