Daniil Medvedev says fitness problems forced him to amend his tactics in the victory over Stan Wawrinka that gave him his first grand slam semi-final.
Medvedev, 23, received painkillers and taping on his right thigh in the first set of a 7-6 (8-6) 6-3 3-6 6-1 victory over the Swiss in the US Open.
He says the injury forced him to play an “ugly” type of game that was less than ideal.
The Russian said: “The way I won was ugly because I am still really painful in my leg. I had to play without rhythm and some games I tried not to run too much.
“I tried not to allow him to develop any rhythm and it worked. I would rather have won by playing a normal game but this is what I had to do.”
The fifth-seed feared from early on he would be forced to retire from the quarter-final injured.
He added: “The first two sets I didn’t have any emotions because in my mind I am losing the match because of my leg.
“Then at 5-2 in the second I thought I was definitely not going to retire because I was going two sets up.
“In the fourth set, I started feeling the painkiller and started moving better.”
Medvedev, who won the Cincinnati Masters in the final big warm-up for the US Open, received heavy strapping to his thigh during a medical timeout when 4-3 ahead.
Three-time Grand Slam champion Wawrinka capitalised to level at 5-5, only for stubborn Medvedev to close out a first set tie-break with three unanswered points.
With his movement improving, Medvedev broke serve in the fourth game to take the second set – although the momentum swung once more in the third as the Swiss 23rd seed raced into a 3-0 lead and saved two break-points to eventually serve out the set.
Medvedev may face Roger Federer, who lines up against the Bulgarian Grigor Dimitrov on Tuesday night, in Friday’s semi-finals and then Rafa Nadal in the final two days later were he to progress.
Wawrinka, who reached the last eight after defending champion Novak Djokovic retired injured from their match on Monday, does not believe Medvedev will be able to topple those two tennis legends.
He said: “He can win the tournament but I don’t think he will. He looks to be tired and has to meet Roger or Grigor [Dimitrov] in the semi and then has another big test in the final.
“But in the past few weeks he has shown that anything can happen.”