Wing-back has adjusted to life in the Premier League after a shaky start and is aiming for an FA Cup upset against Manchester United

Anyone who has seen Matt Doherty play in recent months will wonder why he was so worried. Wolves are seventh in the Premier League and on Saturday night at Molineux they play Manchester United in the FA Cup quarter-finals with a fair chance of reaching the last four for the first time since 1998.

Doherty will almost certainly start at wing-back against Ole Gunnar Solskjær’s team, having zoomed up and down Wolves’ right flank throughout this season. Yet the way the Irishman tells it, after a few games of this campaign he feared he was out of his depth.

“You go through little periods where you’re half-thinking: ‘I can’t play here,’” Doherty says. “[The Premier League] is so quick. You’re just thinking: ‘This is sharp.’ You get the ball and someone is on you straight away. It’s a different level altogether.”

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Doherty is accustomed to overcoming doubts. He was rejected by 15 English clubs during his teens before Mick McCarthy paid £75,000 in 2010 to bring him to Wolves from Bohemians in his native Dublin. At first he struggled and was loaned out but he gradually established himself, becoming an integral part of Wolves’ climb from League One to the top flight. After winning promotion to the Premier League, he fretted he might have reached a level he could not handle.

“People think the step-up is not that big but having done it, I can say it really is that big. I didn’t start the season that well. I had a few performances that weren’t great and I scored an own goal against Leicester [a 2-0 defeat in the second match of the season]. You start to think about things and question yourself. Your confidence isn’t the highest.”

The turning point came when Wolves travelled to West Ham in early September and won 1-0 thanks to a last-minute strike by Adama Traoré. “The West Ham game was where something switched. I just played well and that gave me confidence. And I’ve just taken that forward. It’s like anything, once you get used to it, you start to get better.”

Facebook Twitter Pinterest Matt Doherty scores against Shrewsbury in their fourth-round replay. Photograph: Catherine Ivill/Getty Images

He says he benefited from the fact the Wolves squad are not as bloated as some others in the Premier League, with the manager, Nuno Espírito Santo, using only 18 players so far. “I managed to get myself together but I guess I’m fortunate I got the time prove myself. The squad isn’t huge, otherwise I could have been taken out before I was able to play well. But there was nobody really to come into my position.”

Anyone trying to oust Doherty would have to replicate his exceptional dynamism. The runs of Doherty on the right and Jonny Castro Otto on the left have been recurring highlights of Wolves’ season. Doherty has scored six goals in all competitions and contributed to many more. “It’s the best season of my career in terms of stats,” says the 27-year-old, who explains he is reaping the rewards of changing his diet. He went vegan for a while but now allows himself to eat fish. “The worst I would have been was about three years ago when I was 95kg [15st]. Now I am 88kg [13st 9lb], so that is a seven kilogram loss. I just felt I needed to be in the best shape possible.”

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Not only have Wolves thrived since promotion, they have done particularly well against the top teams, knocking Liverpool out of the FA Cup and beating Chelsea and Tottenham in the league while drawing with Manchester City, Arsenal and Manchester United.

“I think when we play against teams outside the top six, they set up to stop us playing whereas a top-six team will just worry about themselves and that probably gives us a bit more freedom. We back ourselves against the big teams and this season we’ve proved we can hold our own against them.”

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He knows the United side who turn up at Molineux are likely to be in a much better frame of mind than the José Mourinho-led one with whom Wolves drew at Old Trafford in October. “I thought it was going to be a lot tougher at the time but they were going through a bit of a period where maybe they weren’t so happy. I remember thinking the atmosphere wasn’t as loud or boisterous as I’d expected. You could definitely feel tension in the stadium. But they’ve turned it around completely, they’re a different club. They’re playing with a lot of freedom, a lot of speed on the counterattack and a lot of confidence.”

Doherty hopes his national team, too, are about to enjoy positive change. After the game against Untied he will join up with the Republic of Ireland for the first matches since McCarthy replaced Martin O’Neill as the manager. “I’m looking forward to working with him again. A lot of where I have got to now is down to him for giving me the chance in the first place.”

He expects McCarthy to prove a breath of fresh air following the unhappy end to the tenures of O’Neill and his assistant, Roy Keane. “I think he will do things differently, I guess he has to change the mood. Maybe not as serious. More relaxed. Not as tense. It was kind of like that at times.”