Andre De Grasse is trying to put on a brave face about withdrawing from the world athletics championships because of an injury, but his coach says the 22-year old will be haunted by the lost opportunity to beat Usain Bolt in his final 100-metre race.

"If you ask him today he is probably sick of the whole Bolt story, I think that was wearing on him a little bit for the last few weeks," De Grasse's coach Stuart McMillan said Thursday. "I think in retrospect, in a few weeks, when he looks back on this, and this was his last opportunity to beat Bolt, that's probably going to be the thing that haunts him the most."

De Grasse pulled out of the world championships on Wednesday after tearing his hamstring during a workout in London on Monday. McMillan said De Grasse had been in excellent shape and there had been no sign of injury during his preparation for the championships that start on Friday in London.

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"We definitely didn't see anything coming," he said. De Grasse had been practising block starts on Monday at a local track and was set to finish his workout with a pair of light 60-metre runs. He pulled up after 40 metres on the first, grabbing his hamstring. McMillan said the injury didn't appear serious at first and De Grasse felt somewhat better. But an ultrasound the following morning revealed a small tear. De Grasse flew to Germany to see a specialist, Dr. Hans-Wilhelm Muller-Wohlfahrt, who confirmed the injury on Wednesday and said it would take up to six weeks to heal.

"I heard from [De Grasse] 10 minutes afterward, he was very stoic," said McMillan, who did not accompany De Grasse to Munich. "He said, 'It's a grade-two tear, it's going to be at least six weeks. I guess we're out.'"

The injury casts something of a shadow over the 100-metre final on Saturday as De Grasse was seen as potential threat to upset world record-holder Bolt, who is competing in his final race. The Jamaican had stirred controversy this week by appearing to criticize De Grasse for showing disrespect.

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"I'm not going to go down that road," Bolt, 30, said when asked about potential contenders such as De Grasse. "The last guy I said was going to be great disrespected me. So I'm not going to say who's going to be great." That was believed to be aimed at De Grasse and McMillan, who suggested at a meet last month in Monaco that Bolt was trying to avoid racing the Canadian.

On Thursday, McMillan said De Grasse has always respected Bolt, but their relationship changed after the Rio Olympics last year when De Grasse came close to beating him in the 100-metre semi-finals. The two turned and smiled at each other and Bolt wagged his finger.

"I think for probably the last five to eight years Bolt has been used to people rolling over for him, and when Andre didn't do that in the semi-final in Rio last year, Andre definitely meant no disrespect by that, but I think Bolt maybe took it a little bit differently and since then the relationship has been slightly different," he said. "But there is absolutely zero disrespect from Andre to Usain."

De Grasse's withdrawal will be a boost for Christian Coleman from the United States, who has run the fastest 100-metre time this year at 9.82 seconds, and will now be seen as one of Bolt's main threats.

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"I just found out about [De Grasse's injury] today and I wish him the best in his recovery," Coleman said Thursday. "He's one of the guys being in contention to medal, but there are a lot of guys also in the field that are very competitive so I can't necessarily focus on that. I just focus on myself and prepare to run my own race."

De Grasse's injury will also be a blow to the Canadian team's hopes at the world championships. Athletics Canada had been counting on bettering Canada's showing at the last world championships in Beijing in 2015 when the team won eight medals. De Grasse would have been a contender for three – in the 100-metre, 200-metre and 4x100 relay. "I think it's going to be very disappointing," McMillan said. "There are two stories here; Bolt's last major championships … and then from a Canadian perspective, this was the opportunity for a Canadian boy to go out there and race and to potentially beat [Bolt] in his last race."

De Grasse was not speaking publicly on Thursday, but he acknowledged his disappointment in a statement released Wednesday. "To not have this opportunity is unimaginable to me, but it is the reality I am faced with," he said. "I am sad to miss this chance, but I am young and will be back and better than ever in the near future."

McMillan said De Grasse will remain in London for a few days and plans to take in a soccer game on Sunday between Arsenal and Chelsea to help take his mind off running.

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"He's basically just shrugging his shoulders and saying, 'Well it happens, I can't do anything about it now. Let's focus on moving on,'" McMillan said. "I think it will really hit him a little harder when the guys line up on Saturday evening and he sees that he's not part of that. I think that's when he'll probably be a little bit more emotional."