Top-ranked Andy Murray headed a list of high-profile departures in the first round at Queen's on Tuesday, with the Wimbledon champion losing to a player who found out he was competing only on the morning of the match.
"I was sitting around yesterday hoping to get a match".
Both men were below par in the fierce heat as they began preparations for this year's Wimbledon, which begins on July 3.
"It's a big blow, for sure", said Murray, whose forehand was particularly errant and had a first-serve percentage of just 55.
Murray was hoping to warm up for his Wimbledon title defence by winning the Queen's title for a sixth time, but instead he succumbed to an astonishing 7-6 (7/4), 6-2 defeat against the world number 90.
It was the Australian's first win over a top 10 player as he began the long road back from playing only one match in 2016.
Murray saved one set point but not the next as another backhand volley dropped into the bottom of the net and the underdog took the frame.
Raonic wasn't the only leading seed embarrassed on a baking hot afternoon in west London as world number three Stan Wawrinka was beaten 7-6 (7/4) 7-5 by Spain's Feliciano Lopez in the Swiss star's first match since being thrashed by Rafael Nadal in the French Open final.
The South Australian, in just his fifth match in nearly a year, following shoulder surgery and groin, abdominal and pec injuries, saved eight break points in the opening set before pinching a vital point on the Canadian's serve in the tiebreak.
"It's a big frustration", said Raonic, who failed to convert any of his nine break-point opportunities.
'I think it's a question of one or two important matches, ' Raonic said after his defeat to Thanasi Kokkinakis at Queen's.
'I should have been a lot more disciplined with myself even if I lose the points earlier to start hitting the ball a bit more aggressively'.
Major shoulder surgery, a torn oblique muscle, osteitis pubis, a torn pec, a bad elbow, a serious groin issue and a back problem - the 21-year-old's medical history reads like a copy of Gray's Anatomy.
Thompson, 23, reached the final of the Surbiton challenger event last week, but took the first set on a tiebreak and then raced through the second. "I felt like some of those issues I was having a long time were still there, and I just wasn't feeling great with my game".