That decision paid dividends when 12 goals in 26 Ligue 1 matches for Rennes in the 2015-16 season prompted Borussia Dortmund to beat off competition from Liverpool to pay around £13m for one of football's most promising talents, a price tag that could eventually be multiplied by 10 should Dembélé fulfil a number of performance-related clauses on top of the initial £97m fee paid by Barcelona at the end of last month.