Reyes, who shot to fame at Sevilla before a switch to Arsenal followed by spells at Real and Atletico Madrid, was on the books with second tier Spanish club Extremadura.
Forty-six-year-old Spaniard, Unai Emery, had previously been manager at Paris St Germain and Sevilla.
The draw for the quarter-finals of the UEFA Champions League took place at UEFA headquarters in Nyon, Switzerland on Friday.
Manchester United suffers a shock exit in the last 16 after Sevilla substitute Wissam Ben Yedder strikes twice at Old Trafford.
Spanish outfit Sevilla eliminated Istanbul Basaksehir from entering the Champions League this season after beating them 4-3 on aggregate over two qualifying matches.
Leicester City sacks Claudio Ranieri as manager nine months after he guided the team to a fairy tale championship in the English Premier League.
Defending champions Real were paired with Borussia Dortmund in Group F alongside Portugal's Sporting and Legia Warsaw of Poland in the group stages draw.
Sevilla beat Liverpool to become first team ever to win Europa League for three years in a row.
Liverpool sweeps into the Europa League final with a victory over Villarreal at Anfield to strike up in a final clash with Sevilla.
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