There are two key questions about Arsenal's win at Manchester City. Was it a turning point? Or will it end up as merely a flash in the pan, a day that told you all the things that could have been?
For years now I've laughed at the phone-in experts grumbling every time the Gunners lost a big game, or merely drew against a side they should have rolled over, about how Arsene Wenger was "tactically naïve".
Quite how a manager could have survived at one club so long if he didn't know what he was doing, much less won three League titles and five FA Cups, I can't imagine. Add in that on the way he's completely rebuilt a club without the benefit of sugar-daddy owners, and Wenger will ultimately deserve to be considered among the all-time greats of the game.
But there's no doubt that this season his teams haven't always performed in the intelligent way they did at the Etihad Stadium. When they threw away a lead at Swansea back in November they were rightly castigated for getting caught with seven players in front of the ball in a gung-ho search for a second goal with 15 minutes left that ultimately led to them conceding an equaliser.
And if you look at the record before this Sunday against teams in the top four of the table it's as depressing as it has always been, a draw at home to Manchester City and defeats to Chelsea and Manchester United.
But Sunday's trip was a different matter. Led by the selfless front running of Olivier Giroud, and the midfield industry of Santi Cazorla and Francois Coquelin, Arsenal out-worked their opponents.
Giroud, according to the EA Sports stats, covered more ground than any player on the pitch while behind him Arsenal continually dropped into a formation with a blanket midfield of five players who smothered City's attacks and cut off the supply to danger man David Silva.
Of course it helped to have Aaron Ramsey looking fully fit again, and Alex Oxlade-Chamberlain's energy made a huge contribution too. But it was the midfield that helped Arsenal's defence to look far more in control. Per Mertesacker had one of those days when you could understand why he's got more than 100 caps for Germany.
The damage has been done in the first half of the season to think about landing odds of 60.059/1 by catching Chelsea for the Premier League title, or even closing the eight point gap to Manchester City for a top two finish.
But Arsenal have a way forward to make you think they could be worth backing at 8.27/1 to retain the FA Cup, or even that this way of playing could give them an extended run in Europe, where they are up to 13.5 to reach the Champions League final.
What Wenger must do now is make sure his players absorb the lessons of how and why they won this game, and apply the same principles when the next big matches come (away to Tottenham on February 7 would be a place to start).
Get the defending right in all areas of the field and Wenger has the players to score goals. Giroud now has seven from just eight starts in an injury hit season, Alexis Sanchez has already reached 18 for the campaign, Danny Welbeck is in the mix - and that's before you factor in that Theo Walcott is quietly returning to full fitness.
Arsenal have the players, and they now have a formula to get the best from them. They key question is how well they will have applied the lessons of Sunday's success.