Stoke City midfielder Glen Whelan rates Cristiano Ronaldo as key to all of Manchester United's success over the last two seasons.

Whelan told the Daily Mail: "Ronaldo is key to them and keeping him is important. He's one of the best players in the world, and if you have someone like that you don't want him going to another team.

"I want him to stay though. I love playing against United and the likes of Ronaldo and Wayne Rooney. They are champions but it is the game you want to play in. They are the best players in the world and you want to test yourself against them.

"That's what makes their success something that players admire, because they have to face the best game opponents bring to the table every week, and they come through it. It's harder than people may think.

"The players they have, and the system of rotation really helps them. They have top quality players sitting on the bench and that has given them an advantage over other teams. To have that talent pool makes them so strong."