LONDON -- If 2023 was the year in which Arsenal proved unable to maintain the pace as frontrunners, their New Year's resolution must be to thrive in the role of chasers.

A 2-1 defeat at Fulham on the final day of the calendar year extends a poor run of form to just one win in five Premier League games, as the team dropped from first to fourth place in a faltering finale reminiscent of last season's title run-in.

Manchester City are course-and-distance serial winners, and so it felt vital to Arsenal's chances of a first title since 2004 that they built up another substantial lead this time around, something City's own sputtering form and engagement at the FIFA Club World Cup gave their rivals the chance to do.

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While Liverpool -- and, remarkably, Aston Villa -- have taken advantage, the Gunners' rhythm has deserted them with results elsewhere ensuring they now sit below City on goal difference and firmly in a five-way scrap for a UEFA Champions League place, let alone the league title.

"We have to look at ourselves in the mirror because today's performance is the worst we have played all season, that's for sure," Arsenal boss Mikel Arteta said. "Painful and a sad day, that's how I would sum it up.

"We had the chance to be top of the table after 20 games with the consistency that we've shown. We haven't managed well enough to earn the right to win the game. Three days ago we lost a game [against West Ham] that we deserved to win; today was a very different story.

"[Against West Ham] we didn't put the ball in the net and they scored the way they did. It's OK. Today, the overall performance was more worrying."

The situation is far from lost given almost half the season remains, but problems are mounting for Arteta, who must wrestle with the fact that his team are 10 points worse off than at the same stage last season.

One of the principal reasons for that is the regression to the mean in the collective output of Bukayo Saka, Gabriel Martinelli and Martin Ødegaard. That trio were superb last season in masking the lack of a prolific No. 9 in a manner that is understandably proving difficult to replicate.

Eddie Nketiah was a peripheral presence after replacing Gabriel Jesus in the starting lineup, registering just 24 touches and completing only eight passes -- both were the fewest number of any player on either team to complete 90 minutes.

Martinelli and Saka did a good job early on of masking that anonymity by helping to give Arsenal the lead on five minutes. The Brazilian made the most of space on the left to burst forward, cut inside on his right foot and shoot. Bernd Leno did well to thrust out his left hand to save, but the ball dropped right into Saka's path, and he converted from close range.

Arsenal were curiously flat afterward. According to Opta, Martinelli did not attempt a single take-on in the entire game, and Saka faded from view.

A trend is forming. Last season, Saka provided 14 goals and 11 assists, with 11.45 expected goals and 5.81 expected assists. This season, he has seven goals (6.87 xG) and six assists (6.53 xA).

Martinelli delivered 15 goals (9.33 xG) and five assists (6.96 xA) in 2022-23. This season, he has two goals (2.51 xG) and two assists (2.87 xA). Ødegaard registered 15 goals (10 xG) and seven assists (7.95 xA) last season, but four goals (3.93 xG) and three assists (4.33 xA) this season.

This is not necessarily to single out those three because there are other factors. For example, Arsenal are suddenly vulnerable at set pieces, having conceded four times from corners in their past six league games. But without Saka, Martinelli and Ødegaard producing to such a high level, it raises questions over whether they possess the attacking strength in depth to finish above City.

"We weren't good enough in ball possession, we gave too many balls away. We didn't have enough rhythm, enough threat," Arteta said. "Defensively we were second best. We could not control the direct play. It was so easy for them to win that first and second ball and have the opportunity to run."

There was a lack of composure in their play when losing to West Ham on Thursday, and while the stats that night provided some mitigation -- amassing 30 shots but failing to score -- no hiding place could be found here.

Fulham were the better team without having to be at their best. With 29 minutes on the clock, Saka lost the ball cheaply and the home side pounced, Tom Cairney fizzing a cross to the far post, where Raúl Jiménez finished smartly to equalise.

The winning goal was calamitous but deserved. Willian swung in a 59th-minute corner that Arsenal failed to deal with, throwing limbs at the ball without conviction and allowing Bobby De Cordova-Reid to finish from close range.

Arteta introduced Jesus and Reiss Nelson in response, but Fulham remained relatively comfortable and in fact could have added a third when substitute Andreas Pereira hit the crossbar with an 88th-minute free kick.

This was the first time in 48 games dating back to New Year's Day 2022 that Arsenal lost a league game after scoring the first goal. That came against City, too.

Five games ago, Arsenal were six points clear of City. Now they are below them with Pep Guardiola's side holding a game in hand, away at Brentford. City are not flawless, but they are excellent frontrunners. Without a league game now until Jan. 20, Arteta needs Arsenal to regroup.

"We certainly need that reset after today because that's going to be in our tummy for a few days," Arteta said. "I repeat: the game against West Ham feels very different, so you can move on. It's football, it can happen.

"What happened today cannot happen again because if you do that we will never have the chance to be where we want to be."