Former Chelsea and England midfielder Karen Carney, who retired after helping the Lionesses reach the World Cup semi-finals this summer, is writing columns for the BBC Sport website, working on Radio 5 Live and featuring on BBC TV this season.
In Arsenal's 2-1 defeat by Chelsea last month, a big factor was the Gunners' lack of fitness.
They conceded both goals in the last 10 minutes of the game and they looked dead on their feet.
That is purely because new manager Mikel Arteta is wanting to play in a similar way to Manchester City, where he worked alongside Pep Guardiola before. It's about high pressing and a lot of aggressive play in the attacking third. You are constantly sprinting.
It makes you wonder how unfit Arsenal were under former boss Unai Emery? That's a worry.
And while you can see that their fitness levels have dramatically improved since Arteta came in last month, to be able to play the way he wants, they will need time to get even fitter.
The two sides meet again at Stamford Bridge on Tuesday, when I'll be doing co-commentary on BBC Radio 5 Live, and it will be interesting to see their progress.
In that last game against Chelsea, Arsenal weren't at the level Arteta needed them to be. They are more used to the training intensity now and they might have adapted more fitness-wise.
Even in Saturday's disappointing draw with Sheffield United, the Gunners covered more ground and put in more sprints than when the Blades beat them 1-0 back in October - so there's signs Arteta is getting more work from his players, if not the results.
Under Unai Emery, Arsenal drew 1-1 with rivals Manchester United in September. They covered a total distance of 108.32km and recorded 95 sprints during the game. Granit Xhaka (pictured left) was the team's hardest worker, running 10.74km. However, under Mikel Arteta, Arsenal recorded a 2-0 win against United in January and covered more distance in total as a team and more sprints. Attacking midfielder Mesut Ozil was the hardest worker, running 11.54km. He was one of four Arsenal players to run in excess of 11km in that match, including all three of the starting midfield'You need good players to execute the plan'
It's strange to see a big club like Arsenal down in 10th.
They are one point ahead of Southampton, who were a club we were talking about potentially getting relegated a few months ago.
But you can see Arteta has been a positive change. Arsenal are more cohesive and there has been such a big shift.
They press high and aggressively and they have players in the right positions. He seems to have a better rapport with the players and a good understanding of the football club and how it is run.
The fans have a good relationship with him too. When he signed for the club as a player, he came in during a tricky period. As captain, he led them to an FA Cup victory and steadied the ship. That's what he will be expected to do as manager now.
You can be a really good manager but if you don't have the players to execute the plan, then you will struggle.
Arteta has good attacking options but he still has weaknesses in central midfield and defence. They still need to bring players in.
Arsenal's results under Mikel Arteta
Bournemouth 1-1 Arsenal (26 December) Arsenal 2-0 Manchester United (1 January)
Arsenal 1-2 Chelsea (29 December) Arsenal 1-0 Leeds (FA Cup - 6 January)
Crystal Palace 1-1 Arsenal (11 January) Arsenal 1-1 Sheffield United (18 January)
Luiz no longer isolated; Abraham needs help
You can see Arteta has tried to build more protection for his defenders since coming in.
I always felt Arsenal centre-back David Luiz - who won six major titles with Chelsea - was very vulnerable and isolated under Emery. The midfielders just left him to deal with counter-attacks on his own on a regular basis.
Matteo Guendouzi was running everywhere in stupid areas and Lucas Torreira was never in his natural position. Granit Xhaka was just everywhere too.
Arteta has come in and told them to stay more central. It's about letting the attacking players do their jobs and keeping it stable in midfield.
Arsenal haven't been as open because Arteta has sorted the midfield, so Luiz isn't on his own. He has more protection because there's more structure in how the team defends.
Luiz will come up against Chelsea striker Tammy Abraham on Tuesday and the 22-year-old England international always looks a big threat.
He scored when I watched them win comfortably against Burnley earlier this month, and he has five goals in his past 12 league games.
Tammy Abraham has contributed to 19 of Chelsea's 39 goals in the Premier League this season (15 goals, four assists)
People might say he's having a bit of a lull because he started so well, scoring seven goals in his first five games, but it's his first proper campaign in the Premier League and he has still scored a third of their goals this season.
The closest player to his tally of 15 in the club is Christian Pulisic with just six goals, so Abraham has been remarkable this season for such a young player.
Teams probably didn't know how to defend against Abraham before, so the opposition have worked him out a bit.
Chelsea drew a blank in Saturday's 1-0 loss at Newcastle, but one thing you can say is they create a lot of chances and they just have to be more clinical.
Boss Frank Lampard suggested he wants to bring in attacking options after that defeat and, as he said, they can't always rely on Abraham to get the goals.
Karen Carney was speaking to BBC Sport's Emma Sanders
Source: bbc.com