Hamann, who played for Liverpool, says Cristiano Ronaldo's move to Manchester United is making his teammates nervous.
Ronaldo came back to Old Trafford for the first time in 12 years last summer, and he had a great start.
The 37-year-old scored twice on his debut against Newcastle, and then in his next two games against Young Boys and West Ham, he also scored twice.
That was not true at first. As the team started to lose and pressure built on Ole Gunnar Solskjaer, there started to be a sense that Cristiano Ronaldo was holding his teammates back from doing well.
It's not clear if Ronaldo is bad for the team or if people are afraid of him, Hamann said.
Hamann also said that Ralf Rangnick hasn't done enough since taking over for Ole Gunnar Solskjaer in December.
He said: "I don't think this United team has an identity that makes it hard for a player to join."
Make sure everyone is pulling in the same direction; right now, that isn't the case.