Perfectly reasonable choice, imo. He wanted to avoid exactly what happened by going with a more defensive setup (Dembele does fuck all defensively). Mendy is also someone who can match Dembele’s speed, so the plan surely was to play a controlled game first and throwing in Dembele in the later stages, when he can do most damage.
Never been a fan of Atléti but I wouldn’t be disappointed to see them win it this season. Feel like they’ve kinda earned one over the last years. Really will be happy with anyone but those jammy cunts from Chamartín.