Gelsenkirchen - With as many as four central defenders out injured, FC Schalke 04 head coach Jens Keller faces the tough task of working out a way to stop an in-form Chelsea FC attack when the two sides meet for their UEFA Champions League opener on Wednesday.

Speaking to bundesliga.com, the 43-year-old former VfB Stuttgart boss gave an honest account of the physical and mental impact Schalke's busy schedule has on both his players as well as himself, and and how he is planning to keep his players match-fit, with an all-important Ruhr derby against Borussia Dortmund loping large on the horizon.

bundesliga.com: Jens Keller, you’re at the start of a three-week run that includes five Bundesliga matches and two UEFA Champions League ties, starting with Wednesday's game against Chelsea FC. Do you focus on each game individually?

Jens Keller: The Chelsea game is obviously a big clash and we’re all really looking forward to it, but of course I'm also looking further ahead to the Dortmund encounter. If you’ve experienced the Ruhr derby and its very special atmosphere you know there's nothing like it. Schalke against Dortmund is the derby of all derbies - no other game comes anywhere near it.

bundesliga.com: How does a coach cope with such a busy schedule?

Keller [laughing]: A series of games within a short space of time is just as demanding for a coach as for a player! Obviously it takes less of a physical toll than for the players but it is a huge mental effort for me too. You have to prepare the team for a new challenge every couple of days; you’re constantly reviewing things and preparing new tactical line-ups. It takes a lot of energy.

bundesliga.com: During these busy periods, how difficult is it to keep the intensity up in training?

Keller: The players are largely in recovery mode in those periods. If you’re playing a game every three days, you will go over tactical points and speak about the next opponents in training. It’s impossible to have the same intensity in training as in weeks when there's only one match.

bundesliga.com: Is a player more likely to get injured when he plays in Europe and even for his country?

Keller: It’s definitely a factor. I read that ‘Kuba’ [Borussia Dortmund winger Jakub Blaszczykowski] has recently suffered another injury having just recovered from a torn cruciate ligament. We ourselves have a lot of players sidelined at the moment. A number of our top players barely had a break in the summer because of the World Cup so they aren’t quite there yet either, physically or mentally.

bundesliga.com: Do you tell your players to play with the handbrake on in training to avoid injuries?

Keller: Certainly not. The team has to train the same way they should play matches. Putting 70 or 80 per cent in during training doesn't work when you need to be at 100 per cent in matches - though obviously we have to careful not to overstrain them.