Jose Mourinho feared Ashley Cole would never become a Chelsea player when transfer negotiations ground to a halt in the summer.
Mourinho paraded his new full-back at the club's training ground in Surrey today.
But the Blues boss admits he thought his long pursuit of the Arsenal defender had failed as the clocked ticked towards the transfer deadline.
Mourinho said: "I had my doubts and, to be fair, I thought he wouldn't come.
"I was working with the club in the last days to try to find a solution because we couldn't go for a season with one single left-back and not even with other people to adapt.
"I was a bit scared about that. I thought he wouldn't join.
"For me it was a surprise when, in the last couple of days, Peter Kenyon informed me of the big possibility of him to come and I was of course very happy."
The Chelsea boss also admits it has been one of the most complicated transfers he had ever been involved with.
Mourinho said: "There is a relation with the quality of the player and the size of the clubs.
"If you want to buy an ordinary player or if you want to bring a player from an ordinary club I think that's an easy job and an easy deal.
"When you speak about big clubs, I think it's more difficult. It was a difficult transfer. But that doesn't matter.
"What matters now is that he is our player."
Cole, 25, trained with his new Chelsea team-mates for the first time yesterday. He had been away on England duty since completing the move last week.
The left-back will go straight into the squad for tomorrow's game at home to Charlton and is available for the Champions League campaign which starts on Tuesday at home to Werder Bremen.
Mourinho said: "He has been with us two days — not much but enough for him to smell the atmosphere.
"He can smell the way we have our relationships and the way we train and the way we prepare matches.
"It is not much, but it is enough for him to have a feeling of his new life."
Chelsea paid £5 million for Cole with William Gallas moving to Arsenal as part of the deal. PA.
