Osaka split with Sascha Bajin in February following back-to-back Grand Slam tournaments wins at the US Open and Australian Open.
The Japanese star headed into this year’s Wimbledon ranked World No 2 but could not get past her first round opponent Yulia Putintseva.
Kazakh star Putintseva won in straight sets on Centre Court to send Osaka packing at the first hurdle.
After the match, three-time men’s singles Wimbledon champion John McEnroe suggested Osaka getting rid of Bajin was part of the reason for her defeat.
“I’m still trying to figure out why Osaka got rid of her coach after winning the US Open and Australia,” McEnroe said on BBC One.
“Maybe he hams it up a little bit too much or maybe he likes the camera a little bit too much.
“We’re all guilty of that, perhaps.
“Usually athletes and tennis players are extremely superstitious.
“There’s got to be other reasons [for her loss], I don’t think Naomi’s very comfortable on grass.
“But just to do that at that stage really doesn’t make any sense to me.”
Meanwhile, former World No 1 Tracy Austin heaped praise on Putintseva, who has now won all three meetings against Osaka.
“It was Putintseva who came out with a clear game plan to not give Osaka any rhythm,” Austin said.
“There were the slices, there were some short balls, there was some high balls, slow balls.
“Nothing was two or three balls the same height at waist level where Osaka just likes to bury those ground strokes.
“So Osaka was bated into extracting these types of mistakes.”