Dortmund's Moukoko ruled out for six weeks
Youssoufa Moukoko will miss both legs of Borussia Dortmund's Champions League tie against Chelsea after he was ruled out for around six weeks with an ankle injury.
The 18-year-old was replaced by Sebastien Haller in the first half of in-form Dortmund's 2-0 Bundesliga win at Werder Bremen on Sunday (AEDT).
Moukoko on Tuesday discovered he suffered a torn syndesmosis ligament and is expected to be sidelined until late next month.
Dortmund sporting director Sebastian Kehl said: "This is tough news for him and for us, especially in the current stretch. We kept our hopes up, but unfortunately he will be out some time."
The teenager will miss the first leg of Dortmund's round of 16 clash with Chelsea on Thursday and the return fixture at Stamford Bridge on 8 March.
A showdown with RB Leipzig is among the Bundesliga matches the Germany international will sit out.
Dortmund boss Edin Terzic will hope Moukoko will be available when his side travel to face leader Bayern Munich on 1 April (AEDT), with a home game against second-placed Union Berlin to come a week later.
Terzic's men are three points behind Bayern in third place and have won six consecutive games since the season resumed.