A calamity keeper or the human wall? Arsenal's Champions League fate could be decided by which version of Gianluigi Donnarumma they face in France on Wednesday.

Will they be thwarted again by the shot-stopper extraordinaire we saw in last week's semi-final first leg, when the giant Italian's long arms ensured Paris St-Germain escaped Emirates Stadium with a 1-0 win?

Or could we see the return of the error-prone flapper who was left clutching at thin air as the Gunners scored from two crosses in a group-stage victory in October, where the 26-year-old put in the kind of unconvincing display that has put his entire future at the club in doubt?

Arsenal have to score at Parc des Princes or they are out, so it probably doesn't help them that Donnarumma's form has improved at the same rate the rest of the PSG team has during their thrilling Champions League campaign.

His supposed weaknesses have lingered longer in PSG's domestic season, however, with another mistake coming in their loss at Nice last week which ended their hopes of an unbeaten Ligue 1 campaign with only four games to go.

Still, if you support England, or even other English teams, you may be wondering why anyone doubts Donnarumma - after all, he has already been the scourge of Liverpool and Aston Villa in Europe this season, and showed the world his prowess at stopping penalties when he helped Italy overcome the Three Lions in the shoot-out that settled the final of Euro 2020.

He has performed plenty of heroics down the years, but PSG fans don't just remember Donnarumma for his big saves because, since he arrived on a free transfer from AC Milan in 2021, there have been plenty of bad errors too.

In any case, much more is expected of a modern-day goalkeeper than just keeping the ball out of the net, and his distribution with his feet is seen as another weakness.

So, does that drop him down the pecking order when we consider who is the best keeper on the planet, or is he just more proof that the perfect all-round player in his position does not exist?

BBC Sport spoke to former England goalkeeper Paul Robinson about what makes Donnarumma special, and asked French football journalist Julien Laurens why PSG are considering replacing him this summer.

At 6ft 5in, Donnarumma's sheer size makes him an imposing figure, physically.

That clearly helps when he is facing a penalty - just ask Jadon Sancho, Bukayo Saka, Darwin Nunez or Curtis Jones - but it is where he puts his enormous frame when he is dealing with shots or onrushing strikers in open play that impresses Robinson more than anything else.

"He's massive, but his positional awareness in his box is excellent," Robinson told BBC Sport. "That's down to the depth perception he has when he is reading a through ball and his understanding of where his line is.

"A lot of goalkeepers get sucked into rushing off their line to try to close down the angle and to close down the shot, and they think they are in a better position further away from the goal. It is something I did myself sometimes, and you find the shot is past you before you are ready.

"What Donnarumma does instead, very cleverly, is stay closer to his line, maybe two or three yards away. Because of his size he knows he can cover most of his goal from there anyway.

"The save he made low down with his left hand from Trossard's shot last week was the perfect example of that, and of him knowing exactly where he is in relation to his line.

"As Trossard runs into the box, if Donnarumma is three or four yards further forward, like a lot of goalkeepers would be, that shot goes past him. Instead, he holds his position, and makes the save on the angle.

"It is a brilliant save and it is his physique that allows him to make it, but also down to his technique and his positional awareness, which is second to none."

While his form has fluctuated, Donnarumma's contract situation is the main reason why his future is uncertain.

He has one year left on the five-year deal he signed when he joined PSG, and has reportedly been in talks about an extension.

According to his agent, Enzo Raiola, Donnarumma wants to stay - but he has been also been linked to a summer return to Serie A, and Milan, with Inter, while it appears PSG may have alternatives in mind too.

"The club are taking their time to decide what to do," explained French football journalist Laurens.

"They like Lucas Chevalier at Lille a lot and Luis Campos (PSG's football advisor in charge of recruitment) knows Chevalier well from when he was there."

Chevalier, 23, is known for his passing proficiency as well as his saving ability and is seen as the future of French goalkeeping. He broke into the senior squad for the first time at the end of 2024, although he is yet to make his senior debut for Les Bleus.

"PSG have not made their minds up," added Laurens. "Can they really get an upgrade on Donnarumma and, if so, is Chevalier that player?

"Any money they get for Donnarumma – maybe £25-30m - would be pure profit, but then it would probably cost around £50m to get Chevalier, so what do they do?

"The problem they have with Donnarumma is not on his line, where he is great - everyone at the club recognises that. It is just I think (PSG boss) Luis Enrique would rather have a good goalkeeper who is better with the ball at his feet.

"Still, it is a difficult decision. Of course it is ideal if you can get everything you need in a goalkeeper, but I am not sure Chevalier has everything yet."

It is Donnarumma's mistakes that have led some PSG fans to lose patience with him, and seen him targeted by the French media, with one performance in particular proving hard to forget.

"He got some criticism recently for Harvey Elliott's goal against Liverpool, which was bad, then he made a mistake when they lost to Nice too, when their first goal went under his arm," Laurens said.

"For a long time, though, he has been seen as just not being good enough at crosses or set-pieces.

"He has tried to work on that, just like he has tried to improve with the ball at his feet, but I don't see much of an improvement with any of his weaknesses.

"I think also he still carries with him his worst moment, the Champions League last-16 tie against Real Madrid in 2022.

"PSG were 1-0 up at the Bernabeu with 30 minutes to go after winning the first leg 1-0 too, but then Karim Benzema kind of barged into Donnarumma, got the ball off him and scored - and then Benzema scored two more goals quickly and PSG were out.

"A lot of fans remember that moment, and they feel that there is another mistake coming somewhere, but every time we see him doing well, that surely gets him more points to stay and have his contract extended than the other way around."

Donnarumma may have his detractors but the stats are on his side - new data ranks him higher than any other goalkeeper in the world.

The CIES Football Observatory Index takes into account the level of games played plus results, and also measures the quality of chances faced at domestic level to look at the how the number of expected goals from those chances compare to how many were conceded.

It places Donnarumma above Yann Sommer of Inter Milan and Real Madrid's Thibault Courtois at the top of a list which has a couple of notable omissions - Liverpool's Alisson and Manchester City's Ederson both fail to make the top 20.

Robinson used a different criteria, including his eyes, to come up with an alternative top three where Alisson does appear, along with Donnarumma.

"For me, Alisson is the best in the world, because he hasn't forgotten the fundamentals of goalkeeping, which are to keep the ball out of the net," Robinson explained.

"Commanding your box, communicating with your back four, stopping shots and dealing with one on ones are all part of that, but he can adapt to the modern way of playing out from the back too, without taking it to the next level like Ederson does.

"Ederson is the best with his feet but for the all-round package there is Alisson, Jan Oblak at Atletico Madrid and Donnarumma, and you can put those three in the same bracket.

"To be the very best you need the right mindset too, and Donnarumma has that. He has played so many games since his debut for AC Milan aged 16 that he is much more experienced than most keepers his age.

"That maturity means he is comfortable on the biggest stage, and can make a difference the way he has done so many times already.

"There is this uncertainty about where he will be next year but I bet PSG are glad they have got him at the moment - if they go on to win the Champions League this season, he will play a huge part in that."