Delbonis shocks Andy Murray at Indian Wells
World number two Murray, scratchy in his opening win over Marcel Granollers on Saturday, gave up a break in the third set to go down 6-4 4-6 7-6 (7-3) to Delbonis at Indian Wells on Monday.
Murray had never faced Delbonis before and was troubled early on before settling, only to give up a 4-1 advantage in the deciding set.
Delbonis completed victory in two hours, 46 minutes at the ATP 1000 event.
With the win, the Argentinian set up a meeting with either Gael Monfils or Albert Ramos-Vinolas in the fourth round.
Murray looked lethargic in the opening set and his errors were capitalised on by the left-handed Delbonis.
Delbonis did not allow the two-time grand-slam champion a look in after claiming a decisive second break in the first set, but Murray fought back to force a decider.
The world number 53 sent a backhand into the net to give Murray a set point, which he converted to level the match.
Murray broke for 3-1 in the third set, only to give that advantage up in the seventh game via a double fault.
A backhand into the net from Murray saw Delbonis break for 6-5, but he failed to serve it out, needing a tie-break to eventually see out his win when the Brit sent a forehand return wide.