Jose Mourinho took to Instagram to express his thoughts following Tottenham's 1-0 defeat at Royal Antwerp on Thursday evening.
Lior Rafaelov's goal in the first half proved to be the difference between the two sides, with Spurs now second in the group behind tonight's opponents.
Mourinho made four substitutions at half-time with Dele Alli, Steven Bergwijn, Giovani Lo Celso and Carlos Vinicius making way, but their replacements did little to affect the result.
Clearly annoyed with the outcome, the 57-year-old reacted by posting a picture on Instagram of himself on the team coach, seemingly reflecting on a poor night at the office for Spurs.
The caption reads: "Bad performances deserve bad results. Hope everyone in this bus is as upset as I am. Tomorrow 11 AM training."
The former Chelsea and Porto manager made nine changes to the side that faced Burnley in the Premier League on Monday night, with Gareth Bale handed his second start since rejoining on loan from Real Madrid.
Harry Kane was introduced from the bench just before the hour mark, but Spurs failed to find the net even with the added power of their star striker, who has scored ten goals in as many matches in all competitions this season.
The result sees Antwerp, who are currently leading Belgium's Pro League after 10 matches, continue their 14-month home unbeaten run.
Spurs return to domestic action this weekend as they face Brighton and Hove Albion on Saturday, before they travel to Bulgaria for their third Europa League group stage match against Ludogorets next Thursday.
Mourinho's side will be facing tough tests against both Manchester City and Chelsea later this month as they look to fire themselves into the Premier League's top four.
