In matches like this, it is crucial not to be left a man down on the pitch. Had Lenglet kept his cool, he wouldn't have received a red card, and Benfica wouldn't have lost. After all, Benfica was the side that started the match strongly; had I watched the highlights without knowing the result, I would have assumed Benfica had won.
Porto finished the first half leading 1-0. In the second half, Benfica managed to equalize despite being down to ten men, but the disadvantage of playing shorthanded eventually saw them fall behind again. Porto won the match 3-1, yet I was more impressed by Benfica's performance.
Benfica is currently trailing by five points, but Porto is bound to drop points as the season progresses.
There are three unbeaten teams in the league so far. Porto and Lisbon are expected, of course, but Santa Clara has been the surprise package. I checked the fixture list, and Santa Clara hasn't played against any of the big teams yet.
Porto would not have won this match had Benfica not been reduced to ten men. Lenglet showed great naivety in this game; while slapping an opponent is an action warranting a straight red card, the referee sent him off for a second yellow card. Up until that moment, Benfica had held significant dominance in the match. Even though Porto was ahead on the scoreboard thanks to Veiga, Benfica possessed greater playing strength.
I believe Benfica has learned the necessary lessons from this match.