Manchester City's second-half performances are becoming a concern for them, and might just end up costing them in the Premier League title race.
After Sunday's collapse from 2-0 up to draw 2-2 against Tottenham, City have now failed to see out three of the past four league games where they have been ahead at half-time.
The other times they have been pegged back for draws since the turn of the year, at home to Chelsea and Brighton, did not see the same dramatic drop-off in performance as in the second half against Spurs.
However, in all three matches they will look back and think they had chances to make the points safe.
The turnaround at Tottenham Hotspur Stadium was down to what both teams were like after the break - a re-energised and fired-up Spurs, with some new personnel and a different system, against what I think was a complacent City side.
Tactics do matter here, of course, and Tottenham stopped City playing through them the way they had in the first half - but what made more of a difference for Spurs in their fightback was the way their attitude and desire was much greater than City's.
In any game, I always believe that if the team with the better players matches the energy, desire and running power of the team with less quality, and wins the important duels, then they will win the game or maintain their lead.
I do not think City lost their way because Spurs suddenly had more quality than them - it was more that Tottenham just wanted it more in the second half.
That is a concern for Pep Guardiola, especially because his team are trying to put pressure on leaders Arsenal.
There are two reasons why a team's levels can drop in the second half of matches the way City's did against Spurs - mental or physical.
While City played a lot of matches in January, they have got a big squad and Guardiola rotates the team, so I do not see that being the issue - I think the problem was more to do with their mindset.
What happened to them against Spurs happened to me as a player, where a game is so easy and feels so comfortable in the first half, you do not expect what is coming.
Yes, you know the opposition will have a little go at fighting back, especially if you are away somewhere, but you just think you are going to have the same dominance and as many chances.
The irony is that, if the game is a bit more even before the break, you are more fired up for the second half, knowing you have got to kick on.
But because City were 2-0 up and probably should have been three or four goals ahead, they were so dominant they probably switched off a bit.
They should not have done, because they have got enough experience throughout their team to know better - but what was most worrying is this is not the first time it has happened recently.
In the first half, City were dominant, dangerous and looked totally composed - exactly the type of performance I was expecting from them.
It was interesting that Guardiola played Antoine Semenyo and Erling Haaland together as a split front two, and the midfield four was quite fluid.
At times when they were building up, Bernardo Silva would drop next to Rodri and Nico O'Reilly and Rayan Cherki would come inside, a bit like Aston Villa do. It caused Spurs all sorts of problems.
Another little tweak Guardiola made which I thought was quite clever was how they pressed Tottenham when the home side had the ball.
Silva was the player who left his position, and the other three midfielders behind him, to join the front two to create the press. It actually led to City's first goal.
Because Spurs were down to the bare bones in terms of their personnel, they had some players out of position and in a system they have tried recently but certainly do not use all the time.
They were at sixes and sevens with who they were picking up, and as the first half progressed I thought it was just a case of how many goals City would get. I just did not see a way Tottenham would get back into the game - but I was wrong.
Cristian Romero had to come off at half-time through illness, which forced Thomas Frank to switch to four at the back, and he changed to a more orthodox 4-4-1-1 shape, with Randal Kolo Muani joining Dominic Solanke up front.
Straight away, the four in midfield narrowed up to reduce the space City had. They could not get through as easily and, as Spurs saw more of the ball, the hosts grew in confidence bit by bit and built their way back into the game.
The duels I spoke about earlier were a big part of that - suddenly the Spurs players were anticipating second balls and winning knockdowns, and winning possession high up the pitch. It was City who were now under pressure and looking nervous.
City lost all momentum and control and, if not for a couple of brilliant saves by Gianluigi Donnarumma, they probably would have been beaten.
Normally if you have controlled the first half and the other team comes at you more after the break, you might face more pressure and concede more chances but you will also have more space for breakaways.
That did not happen for City against Spurs, even though Frank had left Joao Palhinha and Radu Dragusin two v two against Semenyo and Haaland as he chased the game. Firstly because Spurs were much more switched on, but also because City's front two were poor.
They did not hold enough balls up, or give enough options in behind. I would expect far more from them in that scenario.
Overall, though, I would not say what happened was down to City being all bad or Spurs becoming brilliant - it was a combination of both.
Spurs did much better but City fell down a few levels. That contrast in performances from them, between the first and second half, was as extreme as I have seen from Guardiola's side in a long time.
City have now only won one of their past six league games, and I think everyone is surprised by their results because they have got so much quality and experience.
The reality about their performances is they are not at the level they should be, with the players they have got.
The reason I can say that is not because of their past title triumphs, it is because in the first half I saw City play like a team trying to catch Arsenal - a team on a mission saying "we're coming after you".
Part of the fall off from them in the second half was self-inflicted - giving the ball away, not winning challenges or second balls. It was very unlike them, because we are used to seeing them manage games so well.
They are not out of the title race yet, because the gap is only six points and Arsenal still have to go to Etihad Stadium.
City are still capable of going on the kind of long winning run that has got them over the line before. But at the moment it looks like there is a mindset issue with some of their players.
Some of them - not all of them - seem to think that, when they go up in games, they are done. That is not how you win the title, and that is not the City we know.
Danny Murphy was speaking to BBC Sport's Chris Bevan.
