Louis van Gaal's side have beaten Tottenham, Liverpool and Manchester City in recent weeks to enhance their chances of finishing in the top four and changing what looked like a difficult first campaign for the Dutchman into a relatively successful one.
After a memorable 4-2 win over local rivals and reigning champions City on Sunday, United face a stern examination at Stamford Bridge.
Neville knows United have played well in recent weeks but admits Van Gaal's system and squad will be pushed to the limit against a Chelsea side looking to move one step closer to the title.
"The tests have been Liverpool and City," he told Press Association Sport.
"This is another test
They have proven themselves, but this is the best team in the country and to go to Stamford Bridge is the toughest test.
"The performances from United in the past month have been absolutely outstanding in any season.
"Forget the fact that in this season they are not going to win the league, in any season the level of performance they have shown in this last month has been of a hard standard."
After a stuttering start to his reign, Van Gaal has answered his critics by finding a formation that suits the players at his disposal and Neville reckons a top-four place is all but sewn up.
"We were always very fixed in our formation," the England coach said of his time at Old Trafford.
"Louis van Gaal through necessity has had to change his formation to get different people in at different times
In the last four weeks he has settled into a 4-3-3
It has worked really well and the players looked comfortable in the system.
"He said at the start of the season that his team would get better, they always get better and he has stuck to his word
He said they would be in the Champions League and I think he will be correct."
Source : PA