The Stamford Bridge boss admits that defensive injuries badly hampered his side's last campaign as John Terry, Ashley Cole and Ricardo Carvalho all missed significant portions of the season.
"We tried to have him last January because we were in big trouble at the time, but it was not possible," said Mourinho.
"But now we have him and we have him because we like him. He's a good multi-functional defender."
Mourinho also believes that the competition for places Ben Haim will bring to the Chelsea squad is nothing but a good thing.
"He is a central defender and he gives us the security we need and the competitiveness we need," Mourinho added.
"We do need multi-functional players in the squad, people that during the season can save my skin when I am in trouble."