Leicester City have made a happy habit of recruiting talent from the lower reaches of French football in recent years. Fousseni Diabaté, making his debut, suggested he may be the next to follow in the footsteps of N’Golo Kanté and Riyad Mahrez with a man-of-the-match performance in this comfortable FA Cup victory.

Signed for £2m from the Ligue 2 side Gazélec Ajaccio two weeks ago, the 22-year-old started wide right in a Leicester team featuring 10 changes from the side that beat Watford last Saturday. It was a selection that prompted questions of Claude Puel before the match. No one was quibbling by the end, however, and after a brace and an assist the Leicester fans were singing Diabaté’s name.

“He played second division in France but I’ve followed him a lot and I thought he could become a good opportunity for Leicester,” Puel said of Diabaté. “I think he has good attributes to play in the Premier League: pace, a good engine. He can make good penetration but also good combinations with his team-mates. It was a good game for him to show his quality and step by step we will see if we can give him some game time in the Premier League.”

Kelechi Iheanacho also scored twice, with Wilfred Ndidi rounding off the scoring and Puel was clear the changes he had made had not shown the competition any disrespect. “I am responsible,” he said. “It’s important to keep a good ambition in the Cup, it is an objective for us. But it is also the case that we want to improve the squad, to give them an opportunity to improve. Also to develop young players. Sometimes there’s a risk but for me it’s important to do this.”

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The team Puel sent out still featured two title winners in full-backs Christian Fuchs and Danny Simpson and also £50m of summer recruits in the shape of André Silva and Iheanacho. Alongside Diabaté there was also an opportunity for the England under-20 star Harvey Barnes, but whatever the names on the teamsheet the attitude from the first whistle showed the combination of strength and confidence necessary for the occasion.

Diabaté opened the scoring in the ninth minute. After Peterborough misplaced a throw-in Silva seized possession and slid in Diabaté with a blind pass. Surrounded by defenders, Diabaté still had a lot to do but managed it comfortably, spinning past his marker and cushioning the ball into the far side of the net with the outside of his left foot.

It was controlled, confident stuff and three minutes later City doubled their lead. Again the home side contributed to their undoing, Chris Forrester giving the ball away in the middle of the park. It was forced forward to Iheanacho on the edge of the box, with options left and right. The Nigerian opted to ignore all of them and, again, a controversial decision was vindicated as he finished low into the net from 25 yards.

Iheanacho doubled his tally on the half hour. Demarai Gray and Fuchs enjoyed a sharp exchange of passes that set the full-back free on the left-hand side. The Austrian had time to size up his cross and whipped a beautiful ball to the far post, where Iheanacho volleyed home.

Facebook Twitter Pinterest Peterborough’s Danny Lloyd slides into a post as he tries to meet a cross. Photograph: Lindsey Parnaby/AFP/Getty Images

The former Manchester City striker has struggled to make an impression in the Leicester first team since joining last summer but he has four goals in his last two Cup games. “I said one month ago we would try to give him some more game time,” Puel said. “He has taken his chance.”

A half-time intervention from Grant McCann rallied Peterborough and they pulled back a goal on the hour through Andrew Hughes after a corner. This only served to refocus the visitors. They regained control of the game through the addition of Ndidi and Marc Albrighton to the field and might have scored more before finally closing out the game in the final knockings.

Diabaté made it four in the 86th minute, firing into the roof of the net after Jonathan Bond had failed to hold on to Gray’s shot after a long run straight through the Peterborough defence. The scorer then turned provider, cutting in from the right and teeing up Ndidi for his own powerful finish.

“We’ve done well to get to this point but we’re under no illusions,” said McCann. “We gifted them two goals and the match was over after 10 minutes. I thought Leicester were outstanding on the day but we were well below par. The big difference for me was the concentration levels in possession; every time they got the ball they had a picture of what to do next. It was a steep learning curve for us, but we’ll take tremendous benefit from today.”