Mueller had defeated ElShorbagy at the Optasia Championships in Wimbledon last week to reach his first semi-final at a PSA World Tour Gold event.

"It was quite an intense game," said Mueller.

"In the best of three format the first game is so crucial.

"When you get that 1-0 lead under your belt, it helps.

"Considering I played very well last week, I'm very happy I could keep that going into this week.

"If you're lower ranked you have nothing to lose and all the pressure is the top seed, and as we saw last night with Paul, the World No.1 losing, it can happen."

Mueller will face Peru’s Diego Elias in the quarter finals.

Elias, who finished runner-up at the Optasia Championships last week, beat experienced Frenchman Mathieu Castagnet 11-7, 11-2.

"He's always been a warrior, I grew up watching him play, he was one of the fittest on Tour," said Elias.

"I tried to make it long at the start, I think it worked.

"I think playing three games in 70 minutes the other day was tough for him and I'm just very happy to be done with this, it's best of three so I was a bit nervous.

"You have to be at your best from the start, you see so many upsets in best of three, so I need to get a really good warm-up and be ready for tomorrow."

In the other quarterfinals, Mostafa Asal of Egypt will take on Wales’ world number eight Joel Makin.

Asal edged out England’s Nathan Lake 11-9, 11-9 while Makin registered a hard-fought 11-7, 12-10 win over Frenchman Baptiste Masotti.