#3 Luck
Coutinho was one of the best attacking players not wearing white tonight at the Camp Nou, cutting in from his usual left-hand side role, wiggling into room and also finding team-mates with his sublime passing ability.
He was a huge headache for Walker-Peters, and Pocchetino eventually had to shift Moussa Sissoko to the right-back slot to deal with the Brazilian better. Despite that and Messi coming on, he still looked Barcelona's most threatening attacking player tonight, and was unfortunate not to get on the scoresheet, having two shots come hit the woodwork of Hugo Lloris.
Whereas in some areas they faced bad luck, in some areas they were extremely fortunate, as Son and Kane weren't at their punishing best, allowing Barcelona and their defense to regroup by making a bad pass or holding on to the ball too long on occasions.
Barcelona was really exposed in the second half, and Tottenham's coach would certainly feel his team should have exploited those deficiencies and came away with all three points instead of settling for just one.