"By the reaction of the player you would think there had been heavy contact. He laddered his sock so it must have been a bad injury.
"But when you've been booked in the first half then you are always treading a dangerous line. It's an expensive lesson he's learned."
The Royals added: "I am disappointed but maybe I would be more critical of our finishing in the first 45 minutes.
"When we were 1-0 up we had some really good opportunities to be more in front. We knew they would make changes at half-time given the quality of their players.
"We knew the changes would ask different questions of us. They played with a lot more depth in the second half and that allowed Frank Lampard to push on for the first goal which was a bad one from our point of view in lots of ways. But their second goal from Drogba was great finish.
"When you go down 2-1 so quickly in the second half all the energy at half-time evaporates. It was hard for us to get into the game and the sending off made it very, very difficult."