Everton have completed the signing of Morgan Schneiderlin from Manchester United, but what went wrong for him at Old Trafford? And can he get back on track under Ronald Koeman?

Morgan Schneiderlin was one of the Premier League's most coveted midfielders when he joined Manchester United 18 months ago. The Frenchman had just helped Southampton to their highest-ever Premier League finish, and the £25m fee seemed reasonable for a player who was also attracting interest from Arsenal and Tottenham.

Schneiderlin had been a key figure in Southampton's rapid rise, and his reputation had grown with every passing season in the Premier League.

Managers came and went from St Mary's, but Schneiderlin was always at the heart of the team. His combative, controlling performances even earned him a place in France's national side.

This season, under Jose Mourinho, however, his circumstances changed dramatically. The 27-year-old was not the only Manchester United player to find himself on the fringes at one point or another under the Portuguese, but unlike Henrikh Mkhitaryan, he found no route back into the team.

He leaves for Everton having played just 11 minutes of Premier League football in six months. He had not been included in any of Mourinho's matchday squads since November. Even Bastian Schweinsteiger, a player who was ordered to train with the reserves at the start of the season, had jumped above him in the pecking order.

Manchester United midfielder Morgan Schneiderlin arrives at Finch Farm Manchester United midfielder Morgan Schneiderlin arrives at Finch Farm

It could be argued that Schneiderlin was not given a fair chance by Mourinho, but he did little to help his cause on the rare occasions he started. He struggled in United's 1-0 defeat to Feyenoord in September, and he had an even more difficult time during their 2-1 loss at Fenerbahce in November.

"Football is not just about quality, it's about effort, commitment, playing to the limits and giving everything," said an angry Mourinho afterwards. Having been hauled off at half-time at the Sukru Saracoglu Stadium, it seemed Schneiderlin was one of the main offenders. Mourinho praised his attitude this week, but it is telling that he hasn't started a game since.

Schneiderlin was seen as a long-term replacement for Michael Carrick when he arrived at Old Trafford, but instead it's the 35-year-old who regained his place as their midfield linchpin. With the dynamic Ander Herrera alongside him and world-record signing Paul Pogba further forward, Schneiderlin was pushed out of the picture altogether.

It was a far cry from his first season at United, when he made 39 appearances in all competitions, but even then there were doubts. Schneiderlin was frequently dropped for their biggest fixtures, and even after a starring performance in United's 1-0 win over Manchester City in March, Louis van Gaal was reluctant to give him too much praise.

"I don't have to say it too loud because the last time I said I am very happy for Morgan Schneiderlin, after that he played not so well," he said. Like Mourinho's comments after the Fenerbahce game, Van Gaal's words hinted at complacency from a player who was used to life as an undisputed starter at Southampton.

Morgan Schneiderlin has not started a Premier League game since May

A bit-part role proved a difficult adjustment, but he will be granted the status he craves by his old boss Ronald Koeman at Everton. "Strengthening the midfield has been a priority for Koeman ever since he arrived, as indicated by the failed attempt to sign Moussa Sissoko," says Sky Sports News HQ's Merseyside reporter Vinny O'Connor.

"In Schneiderlin, they've seen an opportunity to sign a player who fits the profile they're after, was prepared to move for the chance of first-team football, and, most importantly, wanted to come to Everton and work with Koeman again. The fact they have worked together before gives both the club and player confidence that he will recapture his best form."

Schneiderlin certainly showed his best form in his previous campaign under Koeman in 2014/15, providing sturdy midfield formations for a team whose defensive record of just 33 goals conceded was second only to champions Chelsea. The Frenchman was the driving force behind their high-flying start to that season, and it was no coincidence that their top-four challenge only fell away when he was injured in December.

Everton looks like a perfect environment for him to flourish again. He partnered Victor Wanyama in a 4-2-3-1 formation at Southampton, and Koeman has adopted the same system at Goodison Park, where Schneiderlin is likely to replace Gareth Barry alongside Idrissa Gueye. On Sunday, he could even make his debut against Manchester City.

He never seemed to fit with Mourinho's plans and Manchester United are unlikely to miss him, but Schneiderlin now has a perfect opportunity to pick up where he left off 18 months ago. With Koeman's arm around his shoulder, it might not be long before he's back to his old self.