When Aston Villa's public address announcer reads out the teams at home games, Emiliano Martinez is introduced as the world's number one. Villa herald Martinez as the World Cup winner he is. Twice he has won the Yashin Trophy, which is awarded to the world's best goalkeeper.

But since his failure to land a move to Manchester United at the end of the summer transfer window, the Argentina international has faced more scrutiny. That may seem curious: After all, Villa are third in the Premier League and in the Europa League last 16. But crucial mistakes have cost Villa as they look to maintain their surprise title challenge.

Sunday's 2-0 win at Newcastle was Martinez's 200th Premier League appearance for Aston Villa and he has kept 59 clean sheets but the 33-year-old appears at a crossroads. Martinez is arguably not as imperious as he once was. But it is difficult to pinpoint exactly why. A World Cup winner with Argentina in 2022, having joined Villa for £17m in 2020, he has been one of the club's best performers.

This season, though, the cracks have begun to show - for which it is easy to blame his failed move to United. An emotional Martinez appeared to be saying goodbye after Villa's final home game of last season, against Tottenham in May. Villa were open to letting him leave, looking at Brentford's Mark Flekken among others, but then Manchester United manager Ruben Amorim lost the battle to bring him to Old Trafford.

United's data suggested Senne Lammens was going to be one of Europe's best, that although he was not good as Martinez now, signing the Belgian made more sense, financially and for the future. They wanted to spend money in attacking areas - signing Matheus Cunha, Benjamin Sesko and Bryan Mbuemo - with Amorim overruled on a move for Martinez as Lammens joined from Royal Antwerp instead.

On 31 August, the day before the transfer deadline, Martinez was left out for a 3-0 home defeat by Crystal Palace. When asked about Martinez's whereabouts, head coach Unai Emery repeated the name of stand-in keeper Marco Bizot several times.

He returned after the international break for a 0-0 draw at Everton on 13 September - with Emery calling him "the best goalkeeper in the world", and one who had a "massive" commitment to Villa. But has Martinez been as consistent this season? There has been more than one late withdrawal from a game - including two following the warm-ups before matches against Brighton and Feyenoord.

He has saved 76.1% of the shots he has faced this season - the most in the league - and is fifth on Opta's 'goals prevented' stats list with 17. He has made 55 saves - the 12th-highest total of any Premier League goalkeeper this season. His 'expected goals on target conceded' tally - which measures the likelihood of an on-target shot resulting in a goal - is 20.85. Villa have conceded 25 this season, but eight of those have been with Bizot in goal so Martinez's stats should not be worrying.

It is the three mistakes leading to a goal - the highest in the league - which will gnaw away, though. The most obvious was his error at Anfield in November, gifting the ball to Mohamed Salah to score, and giving Liverpool a platform for a 2-0 win. Yet, Villa went on to win their next 11 games, before losing 4-1 to Arsenal on 30 December, when Martinez again faced scrutiny.

He spilled the ball under pressure from Gabriel from a corner, allowing the defender to score, although Villa argued the goal should have been disallowed for a high elbow by the Arsenal man. Last Sunday's his mistake, failing to catch or clear Dwight McNeil's shot, contributed to Thierno Barry's winner for Everton.

He missed Thursday's 1-0 Europa League win at Fenerbahce with a calf injury, with Bizot keeping his fifth clean sheet in 11 games this season. Dutchman Bizot, signed from Brest in the summer, is 34 and not a long-term replacement for Martinez. But the Argentine is being linked with Inter Milan, and Villa are expected to assess his future in the summer.

Martinez has made 234 appearances for Villa, with who he is contracted until 2029. He has had a tough season - something former England goalkeeper Paul Robinson sympathises with.

"You're the first one to know that you're not playing well," he said. "It's a confidence position. You have to give out the persona of somebody who's hugely confident and very calm in that team environment, regardless of what's going on inside. "You're probably a mess inside - which sometimes goalkeepers who lack confidence are when they go on to a field. You know what's what's going on inside your body. "But you cannot give that image up anywhere inside the stadium. It's difficult to explain because it's a very lonely position at times. Sometimes you see the ball and it's the size of a beach ball. Sometimes you see the ball and it's the size of a golf ball."

Martinez remains Emery's number one - with some kind of resolution coming in the summer. "I just think it's been running its course for a while now. The speculation has never gone away," Robinson told BBC Sport. "They weren't in a good place, but the lure of Manchester United for him at that time seemed like it was going to happen. "It just seems this season the focus has been diverted slightly, away from Aston Villa. "I'm not so sure he is as settled as he was. There may have been a little drop off. "He's a top quality goalkeeper. Would I class him as one of the world's best? I'm not sure I'd put him in that bracket but if Villa are looking to move him on or he wants to move, they have a problem."