Clarke takes his West Brom side to Stamford Bridge on Saturday, where he will go head-to-head with his former boss and take on a side for whom he made more than 300 appearances as a player.
Mourinho insists he knew Clarke would be a managerial success because of his background in the coaching game and the workload he took on under Avram Grant, Gianfranco Zola and Kenny Dalglish when he left Chelsea.
"We have stayed in touch but have not been speaking about our jobs directly," Mourinho said of Clarke.
"He had a good experience with me but he had a good experience during his playing career. He was always very focused and very organised.
"In other cases for sure he was more than an assistant coach, he was in control of training sessions and match preparation so he had very good experience and when he became a manager for the first time he was very well prepared.
"I knew he would do very well and I'm so happy with that. He knows that every match he plays I am with him and wishing that he wins, but tomorrow is obviously not the case.
"I'm of course very happy to meet him, before and after the match it will not be the same thing to play against Steve than against any other manager."
The Baggies have only lost once in their past seven Premier League games, a run that includes a 2-1 win against champions Manchester United at Old Trafford.
Mourinho knows his team, who are second in the league table going into the contest, will be in for a difficult afternoon.
"He is very good," Mourinho added. "He organises his team very well from a defensive point of view and it is very difficult to play against his team because they defend so well.
"They are always a difficult team and this season we have simple examples, they stopped Arsenal winning and won at Old Trafford, Steve's teams are always difficult."