However, Brazilian striker Jonas is a doubt after missing Monday's training session. Dortmund's form has faltered since December, with the German side winning just two of their previous nine games in all competitions. They have only lost once in that time - Saturday's defeat by Darmstadt - but Dortmund boss Thomas Tuchel is hoping for a convincing win in Portugal to revive their campaign. "We were simply a long way below our limit and we have to admit Darmstadt deserved to win," he said. "In all honesty, we come into our own when it's a 50-50 game.