Marin Cilic has gone from a "small ant" fighting the system to a US Open semi-finalist in the space of 12 months.
A year on from the lowest moment of his career, Cilic defeated Tomas Berdych to reach the last four at a grand slam for the second time.
Cilic dominated the match against sixth seed Berdych to win 6-2 6-4 7-6 (7/4) and set up a last-four clash with either Roger Federer or Gael Monfils.
The Croatian was not in New York 12 months ago. Instead he was serving a provisional ban after failing a drugs test.
The news had leaked out but the International Tennis Federation, which runs the anti-doping programme, would not confirm it until Cilic had been found guilty of an offence.
That came in September and he was banned for nine months.
He appealed to the Court of Arbitration for Sport, which reduced the suspension to four months, and Cilic has been making up for lost time ever since.
The 25-year-old said: "(Last year) I was back in Croatia and I was training. I was preparing for a time when I'm going to play. Definitely it was a difficult period. I didn't know when I was going to start back.
"But it was also a good period for me. I matured a bit more and I was working day after day. I wasn't relaxing and doing nothing. So I think that helped me to improve physically.
"(When I came back) I felt that I was more happy, I was enjoying much more being on the tennis court and still working hard for it. I was tougher with myself in preparation and during the matches, clearer with my goals.
"It's worth more now."
Cilic accepted he was culpable to a certain extent after his mother bought him glucose tablets over the counter in Monte Carlo that, unbeknown to him, contained a banned substance.
But the Croatian did not think the offence merited a ban, particularly because by the time he took the doping test at the Munich Open, he only tested positive for a metabolite of the banned substance rather than the substance itself.
He said: "It angered me how all the process went because it was not fair to me. It wouldn't be fair to any tennis player. So that was just very bad memories.
"But when you're against big organisations, you are a small ant. You can't do much. So I just accepted it. When I came back to the tennis court I erased it from my memory."
Cilic has risen from a low of 47 in the rankings in October back to 16 and will climb further to at least 13 after this tournament.
Earlier this summer he beat Berdych on the way to the quarter-finals at Wimbledon, where he led Novak Djokovic by two sets to one before losing.
Now he has gone one better and it was thoroughly deserved against a lacklustre Berdych, who has had a disappointing summer.
Cilic, whose previous slam semi-final came in Australia in 2010, is the first Croatian man to reach the last four at the US Open since his coach Goran Ivanisevic in 1996.
Berdych accepted he was significantly second best and rued a bad serving day.
"It was horrible from the beginning," he said. "That's impossible to play with an opponent like Marin. I would probably struggle with 80 per cent of other guys if I served that bad like today."
The Czech, meanwhile, revealed he is hoping to lure Ivan Lendl back to coaching following the end of his successful partnership with Andy Murray in March.
"I think it just needs probably the right time and timing to make it happen," said Berdych. "I hope the time is going to come."