BERLIN, Dec 17 (Reuters) - Schalke 04 forward Ibrahim Afellay will be missing in their German Cup round of 16 tie against Mainz 05 on Tuesday when newly installed coach Jens Keller bids to start with a confidence-boosting win. Dutchman Afellay has been nursing a muscle injury for weeks as Schalke have slipped down to seventh in the league, triggering the sacking of former coach Huub Stevens on Sunday a day after their 3-1 home defeat to Freiburg. Keller was named as the new coach until the end of the season. ... More...