Shakhtar Donetsk manager Mircea Lucescu believes David Moyes’ squad rotation has harmed Manchester United this season.
The defending Premier League champions have lost three of their first six Premier League games and were beaten 2-1 by West Bromwich Albion on Saturday when Robin van Persie and Marouane Fellaini came off the bench, Patrice Evra was an unused substitute and Nemanja Vidic and Rafael da Silva were omitted altogether.
And Lucescu, who has won seven Ukrainian titles in his nine years at Donetsk, believes Moyes’ tinkering is a reason for their struggles.
The 68-year-old Romanian, whose side host United in the Champions League on Wednesday, said: "There will always be a change of philosophy under a new coach and every coach needs time to work in a proper way.
"This is why David Moyes is facing difficulties at this stage. But we have analysed the United games and we noticed there are always changes in the squad, maybe four or five players [in each game].
"This rotation means the links between the players can be affected and I think turnover can cause a lot of problems sometimes. We have also discovered that here. The other big teams in the English championship, such as Chelsea, Liverpool and Arsenal, are not rotating the team as much as United and maybe that is a factor.”
Moyes remains adamant that he can restore United to winning ways after the troubled beginning to his reign at Old Trafford.
United have made their worst start to a campaign since 1989, but Moyes takes heart from his record at his former clubs, where poor spells were invariably followed by a revival in their fortunes.
"I have been in situations very similar to this at my old clubs Everton and also at Preston," he told his pre-match media conference at the Donbass Arena.
"You get on and you do the right things. I haven't changed what I have done. I will continue to do that. The results will come. I have no doubt about that."
Moyes accepts that United’s huge fanbase and profile means that every defeat generates plenty of headlines.
“It is always the thing at Manchester United," he added. "Everyone is interested in them. It is a talking point for everybody throughout the world.
“That is why it is, for me, the greatest club. It is a great honour to be the manager. Even our arrival here in Donetsk has been greeted with a lot of supporters at the airport. It is a great thing.”
The United manager could bring Robin van Persie back into the starting XI after the Dutchman, who had missed the previous two games with a thigh problem, came off the bench in the loss to West Brom.
“He is fit,” said Moyes. “We will make a decision whether we start him. He is as good as anybody I have seen. His football common sense is fantastic and he is a great goalscorer.”
Moyes is certain to make at least two more changes in Ukraine with centre-back Rio Ferdinand and midfielder Anderson, two of those who started against West Brom, not even in the travelling party.
Several others are anticipated, with striker Van Persie and full-backs Evra and Rafael also likely to start while wingers Antonio Valencia, Ashley Young, Ryan Giggs and Danny Welbeck offer alternatives to Nani and Shinji Kagawa.