But Messi - who else? - would add two more goals before the match was over.
Have you ever watched Lionel Messi line up to take a free kick, and not think that he's definitely going to score?
MESSI's second goal was a first time touch.
Ousmane Dembele doubled the lead with an outstanding individual effort and Messi fittingly had the final say, completing his hat-trick by scoring either side of a red card for Samuel Umtiti.
Messi's first goal came with a attractive free kick in the 32nd minute at Camp Nou Stadium.
Messi's treble against the Dutch champions was his eighth in the Champions League, moving him clear of Juventus' Cristiano Ronaldo with seven, as the player to have netted the most hat tricks in the competition.
But Barca's second did eventually come in similarly superb style.
In the other Group B game played on Tuesday, Inter Milan scored two late goals, including a stoppage-time victor, to mark their return to the Champions League with a 2-1 comeback victory against Tottenham.
Mauro Icardi's superb volley levelled the scores in the 86th minute and Matias Vecino headed a stoppage-time victor at the San Siro.
'The injury made the first year hard for him.
There were dramatic late goals around Europe, including for Inter Milan against Tottenham Hotspur, and winning starts for several of the leading contenders, with Atletico Madrid battling back to beat Monaco.
On 13 minutes Porto were awarded a spot kick but keeper Ralf Faehrmann picked the right corner and spectacularly palmed Alex Telles' penalty to safety.