Injuries harmed the Blues as they surrendered the Premier League title to Manchester United last season.
Captain John Terry and left-back Ashley Cole missed long periods of the campaign and centre-back Ricardo Carvalho was also out for a number of important games.
Israel international Ben Haim will offer extra cover next term after moving from Bolton on a free transfer.
"We tried to have him last January because we were in big trouble at the time but it was not possible," said Mourinho from the club's pre-season training camp in Los Angeles.
"He was an important player for Bolton and they wanted to keep him until the end of the season.
"But now we have him and we have him because we like him. He's a good central defender but also a good multi-functional defender.
"He can play right-back and left-back in case we have the need and during the season, so we're very happy to have him.
"I'm sure about his qualities but after three training sessions together it's even easier to know the player and after six hours training together I like him even more."
Mourinho feels Ben Haim will also bring important competition for places in central defence, where Terry and Carvalho have been the mainstays over Mourinho's three seasons in charge.
Mourinho said: "Tal is not a right-back in the same way that (Michael) Essien is not a central defender, but he had to play there last season for a long time in the same way that Paolo (Ferreira) is not a centre-back and we sometimes had to play him there.
"He is a central defender and he gives us the security we need and the competitiveness we need. Before it was Terry and Carvalho and nobody else and now we have three central defenders of quality and they will have to compete between them.
"But we do need multi-functional players the squad, people that during the season can save my skin when I am in trouble.
"So what Essien and Paolo did for me last season and many other players playing in different positions, is the same thing Tal will do for me."
Ben Haim may have to show his flexibility as early as Saturday in the first game of Chelsea's three-match tour of the United States against Mexicans Club America at the University of Stanford in northern California.
Mourinho saw left-back Wayne Bridge fail to complete Chelsea's first training session on Tuesday as he failed to shake off a hip injury sustained on England duty in May.
And with Cole not due to start training until next week following knee surgery and unlikely to play until the Blues return to Europe, the Chelsea boss already has some shuffling to do.
"We don't have a competitive game in the next few days but at the moment I have no Bridge or Ashley Cole," Mourinho said.
"There is a hypothetical situation where we have a game tomorrow and I need a left-back and I have to choose between Tal or Paulo or Glen Johnson. So it's very comfortable for a manager to have these kinds of players in the squad."
Mourinho believes his squad is in better shape than a year ago with only Michael Ballack staying in London to recover from surgery and new signing Claudio Pizarro of Peru being given extra time off following the Copa America.
"Last year was a disaster because we started the season with half a team," he said. "And after that, every two to three days, some players arrived depending on their performance at the World Cup.
"We had players who were out in the last 16, out in the quarter-finals and then finally the Portuguese and the French guys because they had reached the semi-final stage. It was a disaster.
"This season we are starting with everybody. Only Pizarro is not here and Ballack with injury.
"Everybody here is working very hard, the motivation is there. Everyone is training like they play, almost, with their attitude, intensity, concentration and strength. The training is becoming very real."