Peterborough United 1-5 Leicester City

Debutant striker Fousseni Diabate and Kelechi Iheanacho both scored twice as Leicester outclassed League One Peterborough to reach the FA Cup fifth round.

Diabate - signed from French side Gazelec Ajaccio - toe-poked in and Iheanacho guided the ball into the corner to put the visitors in control.

Ex-Manchester City forward Iheanacho volleyed home Christian Fuchs' cross for a 3-0 half-time lead.

Posh improved after the break, pulling one back through Andrew Hughes, but Malian Diabate and substitute Wilfred Ndidi struck late on for the Foxes.

Kelechi craves the Cup

Premier League Leicester had Jamie Vardy and Riyad Mahrez on the bench but did not need to call on either, while Shinji Okazaki was left out of the squad altogether,

A side showing 10 changes proved more than strong enough as the Foxes' fringe forwards thrived.

Demarai Gray and academy product Harvey Barnes played their part but it was Diabate and Nigerian Iheanacho who did the damage.

Diabate was lively throughout and slotted effortlessly into a fluid front four, while his strike partner now has braces in consecutive FA Cup ties after also scoring twice in Leicester's replay win over Fleetwood in the third round.

Iheanacho is yet to score a league goal since his £25m summer move but has scored nine FA Cup goals in nine ties since January 2016 - more than anyone else.

Iheanacho joined Leicester from Manchester City for a fee understood to be £25m last July

Unhappy milestone for McCann

While Manchester United boss Jose Mourinho marked his 100th game in charge in style on Friday with a 4-0 win in Yeovil, Peterborough manager Grant McCann could not follow suit as he reached the same milestone.

The storyline was there - the former Northern Ireland international had scored the winner for Posh the last time the sides met in 2013 - but a slow start took the tie beyond them.

While the 2015-16 Premier League champions were good, the hosts' Chris Forrester gifted possession for Iheanacho to calmly slot in to make it 2-0.

However, Jack Marriott, Danny Lloyd and Marcus Maddison showed the attacking flair they are capable of in the second half and Hughes' goal on the turn was the first Leicester have conceded in six games.

Peterborough now turn their attention to a League One play-off battle, with them four points behind sixth-placed Rotherham going into Saturday's 15:00 GMT matches.

A run of only five defeats in 23 games in all competitions, coming into this tie, suggests they could yet achieve promotion back to the second tier.

'Diabate can do well in the Premier League'

Peterborough manager Grant McCann told BBC Sport:

"It killed the game - when you're playing against a team of Leicester's quality and for us to gift them two goals in the first 10 minutes is heartbreaking really.

"We could've done a lot more in the first half - we were poor and probably lucky to come out 3-0.

"We gave a better account of ourselves in the second half, I think you saw glimpses of what we can do but disappointing for them to get a couple of goals when they didn't really test us too much."

Leicester boss Claude Puel told BBC Sport:

"It was a tough game at the beginning with the rain, wind and a small stadium - they're all good ingredients for a cup game."

On Diabate: "No-one knew him as he played in the French second division but I followed him a lot and I saw today he can become a good opportunity for Leicester as he has the attributes to play in the Premier League."

On Iheanacho: "I think he's improved since the beginning - he's clinical, he has quality and a good attitude. I'm happy for him and the squad of course."

Rare breach for Foxes defence - the stats

• Leicester have progressed from seven of their past eight FA Cup fourth-round ties against lower-league opposition, with their only defeat coming at the hands of West Brom in 2001-02 (0-1).

• Peterborough have failed to keep a clean sheet in any of their 32 FA Cup matches against top-flight opposition.

• Kelechi Iheanacho has been directly involved in 10 goals in nine FA Cup appearances (nine goals, one assist).

• Fousseni Diabate (two goals) scored nine minutes into his Leicester City debut and was the first Leicester debutant to score since Nathan Dyer in September 2015.