England Under-20s manager Paul Simpson has admitted to being perplexed by the referee's decision to dismiss Josh Onomah during the World Cup quarter-final win over Mexico Under-20s.

The Young Lions were sitting on a one-goal lead when the Tottenham Hotspur midfielder was shown a second yellow card for accidentally treading on opponent Juan Aguayo with 18 minutes still left to play at the Cheonan Stadium.

England were able to get themselves over the line to set up a meeting with their Italy counterparts in the last four - the first time they have reached that stage since 1993 - but Simpson was left ruing the decision to dismiss Onomah which automatically rules him out of the semis.

"It was an incredible decision to send Josh Onomah off. I have no idea what the referee saw," he told reporters. "We now have a player suspended for a World Cup semi-final game for a decision that is absolutely ridiculous.

"It was a really tough game against an excellent Mexico side and I'm absolutely delighted to get through. We defended for our lives when we had to. We created some really good chances in the attacking phases, but we just didn't quite have the finish. Unfortunately at the end we had to dig in, with backs against the wall.

"Sometimes in big games, and this was a huge game, there is a little bit of nervousness, so I think we just had to get through the first half to be able to play the second. Sometimes you just have to get a foothold in the game and we came out and started the second half really well. We were pressing, closing down, we turned them round and got people running in behind through some really good football.

"The big difference was we came out with a little bit more belief and cast away those nerves that were a little bit evident in the first half and I thought it was a good performance."

Liverpool-bound forward Dominic Solanke proved to be the matchwinner for England, scoring the game's only goal two minutes into the second half.