Manchester United defender Axel Tuanzebe was spotted wearing a fitness tracker during Tuesday night's 2-1 defeat against Leicester.
The United man played the full 90 minutes in the defeat at Old Trafford, which handed their arch-rivals City the Premier League title.
Eagle-eyed fans spotted that Tuanzebe was wearing a black strap on his wrist concealed by his sleeve throughout the match.
What's a WHOOP strap?
More than a standard fitness tracker, the Whoop Strap is useful for athletes and anyone else who wants comprehensive insight into their daily activity and health, with personalized coaching to help optimize training and sleep.