Final four all have questions to answer
With Chelsea slipping and Spurs on a high, FA Cup semi-finals should be informative
How strong is Chelsea's mentality? There will have been a lot of soul-searching at the club after the defeat at Old Trafford. I know how it feels to lose a major game in the latter part of the season - it can generate uncertainty about strategies that have not been questioned up to that point. You need to have a strong mentality to push through it and get back to the basics of winning matches.
Watching the game, I was struck at how subdued Antonio Conte was on the touchline. His passion and energy have often worked with his team, as if the two power each other on, but against Manchester United he was a quieter presence.
Chelsea have led the way this season and there is no reason why they cannot win this FA Cup semi-final against Tottenham, although it is perfectly balanced between the league's two top teams, with the chasing party in the better form.
It goes without saying that Chelsea will need all the players hit by illness to have recovered this week and the news about Gary Cahill will be troubling.
I was surprised at the timing of John Terry's announcement on Monday that he was leaving at the end of the season. Did it have to be then? When Marcos Alonso pulled out of the United game in the warm-up I wonder if the captain felt that his time had come to step back into the team.
Especially on such a big occasion he would have been confident that he had the experience to do that, although no defender would have had an easy time from United that day. Instead Conte opted for Kurt Zouma and that might have made up Terry's mind.
Can Spurs cope with expectation?
The league's in-form team must believe that they now have the chance of the club's first FA Cup in 26 years. They are a young side on the whole and many of them would not yet have been born in 1991 when the club last won the FA Cup at Wembley but that is not to say that they will be immune from the pressure of a run like that.
When I broke into the Manchester United team as a teenager, I was only too aware of how long it had been since we had won the league title - it was a 26-year gap in the end. Of course, one group of players cannot bear the responsibility for all those years of failure but equally the only way to stop people going on about it is to win the trophy in question.
When United blew the old First Division title in 1992, we came back that bit more determined the next season to make sure we won it, and we also had the experience of going close. Spurs had a similar experience last season when they went for the title and it was Chelsea who ultimately stopped their charge, although they were struggling to catch Leicester City even before then.
The energy and the aggression that Spurs have shown in recent weeks has been impressive.
Mauricio Pochettino has to decide whether he matches up with Chelsea's three-at-the-back system but either way his team seem to switch from one formation to the other pretty seamlessly.
Tottenham have not played well at Wembley this season in the Champions League and that is another consideration for them to deal with.
Will Wenger stick with three at the back?
A lot depends on how Arsene Wenger decides to approach the Manchester City game tactically and he is a manager who generally sticks to his core principles. Before this season, Arsenal had two wins and two draws against City over the previous two league seasons plus a win in the Community Shield. They beat City 2-0 at the Etihad Stadium in January 2015 when Santi Cazorla, still injured, was outstanding.
It was interesting to see Wenger switch to a three-man defence against Middlesbrough on Monday. Managers make sudden changes like that when they have the time to work on it in training, as Arsenal did, and also to refocus the minds of players on the job in front of them.
It also felt like he was trying it out with tomorrow's FA Cup semi-final in mind, and perhaps the win against Middlesbrough will convince him that it is the right way to go against a much better opponent.
I rate Alex Oxlade-Chamberlain as a wing-back; in fact I think he has the kind of versatility that Antonio Valencia has demonstrated in switching from winger to full-back. There is inevitably a lot of focus on Alexis Sanchez, and his effect on the other players. I have to say that I would like to have played alongside him. He gets upset when the team lose. He demands high standards of his team-mates. There is nothing wrong with that.
Sanchez likes to lead the press and you can sometimes see him waving his team-mates forward to join him, and how Arsenal tackle that side of the game will be a major part of whether they are successful or not.
Can Manchester City deal with high-pressing opponents?
Which brings us on to City, who will have watched the Arsenal win on Monday with interest. How will Arsenal set up against them? It can be a nightmare when you do not have a clear idea of how an opponent is going to play, especially given that Arsenal have been fairly consistent in that regard for a long time.
Pep Guardiola's team usually face three different strategies from opponents trying to stop them from passing out from the back. There is the full press, with no holds barred, straight on to the first ball out from the goalkeeper.
Some teams press the second pass, perhaps allowing it to go to a centre-back who is not so sure of his own distribution. The last option is giving City half the pitch and just stepping up to meet them when they cross the halfway line.
I was a Uefa technical observer for City's home tie against Monaco and they were pressed ruthlessly by a very quick, young, energetic side. City won the game but the damage was done for the second leg. When City start passing out from the back you can sense the nerves in their own fans but the team never stop trying. A lot depends on how Arsenal come at City and, of course, how Guardiola's men then deal with it.
(© Daily Telegraph, London)