It has taken Erik ten Hag one season to put Manchester United back where they belong – in the Champions League.
After starting with two defeats, followed by Cristiano Ronaldo's acrimonious exit and a record 7-0 mauling at arch rivals Liverpool, Ten Hag deserves huge credit for steering United to a top-four finish.
Next season the challenge will be to try to close the gap on champions City, which currently stands at 17 points, too big a gap for United to be considered title contenders next term, even if they land top transfer target Harry Kane this summer.
But a top-four finish, a first trophy in six years in the Carabao Cup and the chance of another one, with the FA Cup final a week on Saturday, represents an impressive first season for Ten Hag.
United midfielder Casemiro provided a timely reminder of his enduring class as United compounded Chelsea's miserable season with another defeat – their 16th in the Premier League.
Casemiro scored United's early opener and ran the game thereafter as Erik ten Hag's side moved up to third, unable to be caught by Liverpool, who are consigned to the Europa League.
Brazil star Casemiro has been instrumental in getting United back to competing with the very best in Europe, his £70million arrival from Real Madrid one of the shrewdest buys under Ten Hag.
Ten Hag refers to the 31-year-old as the “cement between the stones” but after his second suspension of the season in mid-March, Casemiro looked flakey on his return a month later.
But a bicycle kick to secure a 1-0 win at Bournemouth last weekend and this marauding midfield display confirmed he is back to his best, with the FA Cup final to come.
If United are to beat local rivals Manchester City and thwart their bid to emulate their Treble of 1999, then they will rely heavily on the experience and influence of Casemiro at Wembley.
Casemiro scored the opener in United's 2-0 Carabao Cup final win over Newcastle in February and he will have to be at the top of his game once again if the City juggernaut is to be halted.
With a top-four place now secured, Ten Hag has the luxury of resting key men like Casemiro for Sunday's visit of Fulham, ensuring he is fully fit to face Pep Guardiola's side next weekend.
For Chelsea, it was a second defeat in Manchester in five days, after their 1-0 loss at City last Sunday continued their desperate campaign, one that cannot end soon enough for them.
United took the lead in the sixth minute, Christian Eriksen curling in a free-kick that was met by Casemiro, whose header left Kepa Arrizabalaga no chance.
Casemiro's fellow Brazilian Antony came off worse in a challenge with Trevor Chalobah midway through the first-half and was carried off on a stretcher, his FA Cup final hopes in jeopardy.
Casemiro played an exquisite no-look lofted pass to Jadon Sancho, who squared the ball to Martial, for the simplest of tap-ins to make it 2-0.
Bruno Fernandes won a penalty in the 72nd minute when he was tripped by Chalobah, which he duly converted to make it 3-0.
Rashford made it 4-0 in the 78th minute, with his 30th goal of the season, the first United player to reach that number since Robin van Persie a decade ago, when the Red Devils last won the title.
Sub Joao Felix grabbed a goal for Chelsea in the 88th minute, but the night belonged to United and Ten Hag, who can consider it mission accomplished in his debut season.
