The Portuguese is keeping his line-up secret for tactical reasons, while he had encouraging words for Samuel Eto'o after the striker broke his Blues duck at the weekend
The Portuguese has informed the veteran centre-half that he will play in Gelsenkirchen but will not disclose the remainder of his line-up until shortly before kick-off.
"I know but the players don't know," Mourinho told reporters on Monday. "[With] only two days in between matches, I didn't train tactically for the game so the players don't know, so it's a principle I want always to keep.
"When they don't know I don't like to say. I have to make an option for tomorrow [Tuesday] - I have to make a choice between David [Luiz] and Gary [Cahill].”
Schalke have won both their opening European fixtures this season, while Chelsea have won one and lost one.
And Mourinho is expecting a tough tie against the side currently fifth in the Bundesliga, especially with left-back Ashley Cole still recovering from a rib injury.
"It's difficult for a team to be at maximum power, to play a match without somebody missing through injury or suspension," the two-time Champions League winner said. "They miss a couple of players but us too.
"Ashley Cole is an important player for us and is not playing. That's not a big deal. A team is a squad, not 11 players, and they have a squad with players to replace.
"What's the difference between [Jefferson] Farfan and [Christian] Clemens or [Max] Meyer, between [Marco] Hoger and [Roman] Neustadter? It's a good team, a good opponent, and hopefully we can be better than them.
"We play now two matches against the strongest opponent in the group and need points over these two matches. That's obvious. Tomorrow we have a game and we want to win and are going to try to win."
Mourinho also spoke of Cameroonian forward Samuel Eto'o, who netted his first Premier League goal for Chelsea against Cardiff City on Saturday.
"Cardiff was good for him, not just for the goal but for his contribution," he added. "His movement was very good; in the first half when Cardiff was compact and closed he was the one in attacking positions with better movement and participation.
"It's the goal that gives him the confidence, the extra motivation he needs, so normally now he is happier. He's a very good player." ------------------ goal.com