To put it more accurately, the defender's ongoing injury is proving to be the deciding factor as without him, the London club's previously solid defensive unit has completely crumbled. Worse yet, coach Mikel Arteta doesn't seem to know how to put it back together.
Before Saliba injured his back in the Europa League last-16 second leg in mid-March, his team was on a roll. In four league games, they conceded only two goals and won all their matches.
Then, the imposing defender (193 cm, 92 kg) got injured in the aforementioned match against Sporting and the change of fortunes was immediately evident. Arsenal lost their lead in the match and were eliminated from the competition, losing on penalties.
Since then, not only have Arsenal not kept a clean sheet, but the number of goals conceded has been increasing from game to game. In five league appearances without Saliba, Arsenal have incredibly let in nine.
Their last three games were all draws. They have only collected three out of nine possible points and they are enduring their longest wait for a win in the league since the beginning of the season. Before the injury, Saliba had not missed a minute in the Premier League, so we can objectively observe his impact.
With Saliba on the pitch, Arteta's team concede an average of 0.9 goals per game, without him, double that (1.8). There is also a noticeable drop in the number of points scored per game (2.4 with him vs 1.8 without him) and their winning ratio of 77.8% has dropped to just 40%.
Their defensive troubles culminated with three goals conceded in their last home game against Southampton on Friday. This is something that simply should not happen to the league leaders in the most prestigious competition in the world.
"We have to look in the mirror, we let in three really cheap goals. When you let that happen, it's extremely difficult to win in a competition this tough. You can't make mistakes like that at this level," said Arteta.
But experts say he should look in the mirror first. For example, Paul Merson, the Arsenal legend and former Arsenal mainstay who won two titles in the late 1980s and early 1990s, criticised the coach for the composition of the side in Friday's match with Southampton.
The Sky Sports TV expert wrote: “Arsenal played Fabio Vieira instead of Jorginho last week, and I thought that was unbelievable.
“They’ve brought Jorginho in to be a calm head in big matches. I didn’t think the game against Southampton was a foregone conclusion, and to keep Jorginho on the bench was a big mistake."
Vieira was having a nightmare on the left side of midfield and Arteta preferred to withdraw him from the field after an hour of play.
Saliba is not the only stalwart that has missed matches recently, though. Swiss midfielder Granit Xhaka fell ill before the last game with Vieira taking his place.
On that selection, Merson added that without Saliba, Arsenal needed more protection for their defence from the base of midfield, which Vieira failed to provide effectively.
“With Holding playing instead of Saliba, Arsenal needed protection from their midfield - not people getting turned. Arteta hasn’t done a lot wrong this season, but he made a mistake there.”
Last Friday's draw has put Arsenal under even more pressure than they were already under, and the advantage now lies firmly with Manchester City. If City win on Wednesday, they will be only two points behind their rivals with two games in hand.
Arteta will be hoping that at least Xhaka will be able to return to the side.
As for Saliba, according to the latest reports, his back injury has turned out to be more serious than first thought and it may be that the Frenchman will not be involved for the rest of the season.
He is said to be comfortable starting with painkillers, but the doctors have threatened that if he did, he could cause permanent damage.
Unfortunately, the towering central defender was supposed to be Arsenal's main weapon in stopping relentless Norwegian striker Erling Haaland.
"How do they stop Erling Haaland?", former great Wayne Rooney questioned in his column for The Times.
"With William Saliba injured, there’s no prospect of matching his pace and power individually, and the only way is to go out and try to impose their own game.
"Arsenal should focus on how to expose those City defenders rather than focus too much on Haaland. The mindset needs to be: nobody thought we’d be here, and now we’re playing for the title - so let’s go and take it."
Vague advice and scant consolation. It seems things don't look so rosy for Arsenal ahead of Wednesday's game and in the title race overall.
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