World number one Andy Murray was knocked out of the Madrid Open as he lost in straight sets to Croat Borna Coric in the last 16.
Coric, 59th in the world rankings having secured his first ATP Tour title in Morocco last month, won 6-3 6-3.
The 20-year-old broke his British opponent three times in the opening set, and a further break in the second was enough to secure victory.
Coric will face either Grigor Dimitrov or Dominic Thiem in the quarter-finals.
Murray, 29, looked frustrated throughout as his testing clay-court season continued.
The Scot lost in the last 16 of the Monte Carlo Masters on his return from an elbow injury last month, and was then
beaten by Thiem in the semi-finals of the Barcelona Open.
“There were a lot of things that weren’t particularly good today,” he told BBC Sport.
“I made a lot of unforced errors and I also didn’t find anyway to make it a more competitive match, so that’s the most disappointing thing for me.
“You can lose matches sometimes, but the manner of today’s loss was disappointing.
“I didn’t feel that was down to confidence – I just wasn’t focusing as well as I needed to on each point.”
“Things can change fast but you need to find exactly what it is that is going wrong and how you’re going to fix that and commit to it. And if I do that, I’m sure I can turn it round.”
Coric lost in qualifying and only gained a place at the tournament as a ‘lucky loser’ thanks to an injury picked up by Richard Gasquet.
This was his second victory over Murray, having also beaten him at the Dubai Championships in 2015.
In a scrappy opening set, Coric broke to lead 3-2 but a couple of forehand errors allowed Murray to break straight back.
Murray, twice a winner in Madrid, then lost his serve once more, Coric comfortably held and Murray was unable to hold his serve to stay in the set.
His frustration boiled over in the eighth game of the second set as Coric won a long rally to break, before serving out the match.
Murray will next play in Rome, where he is the defending champion.
Djokovic through to quarter-finals
World number two Novak Djokovic reached the quarter-finals with a 6-4 7-5 defeat of Feliciano Lopez.
Defending champion Djokovic, who recently split with his coaching staff, had few problems against the 35-year-old Spaniard.
Belgium’s David Goffin is also through to the quarter-finals after beating Milos Raonic 6-4 6-2, while Kei Nishikori saw off David Ferrer 6-4 6-3.
Rafael Nadal plays Australian Nick Kyrgios later on Thursday.