Shakhtar Donetsk coach Mircea Lucescu says Manchester United's poor form means nothing ahead of Tuesday's clash at Old Trafford.
David Moyes has been under increasing pressure with United suffering two straight losses to slip to ninth in the English Premier League.
But Moyes' men top Group A in the UEFA Champions League and Lucescu warned his team United were a different prospect in European competition.
"Even though they are not playing well, these are two different competitions and you can't really compare them," he said.
"In the Premier League, the English teams know each other and the teams they are playing, but with the Champions League it is a totally different situation.
"For Manchester United it is a must-win match as they want to win so they can top the group and for our part we are going to play our best as it is important for us to progress as well."
Lucescu expects Moyes to rotate his squad with an eye to Sunday's Premier League trip to Aston Villa, but said even then United were a strong side.
"Every manager knows their squad back to front and each individual player, and each manager has his own style," he said.
"Some prefer to rotate to keep the squad fresh and some prefer to keep the same team.
"In David Moyes' case he likes to rotate his team but the squad is very strong and therefore the quality of the players doesn't diminish."
United suffered a 1-0 loss at home to Everton on Wednesday before slumping to a 1-0 defeat against Newcastle at Old Trafford on Saturday.
Lucescu noticed United had 'lost their spark' against Newcastle, but believes they were still close to taking something out of the clash.
"When they were playing Everton it was David Moyes' former team so they were playing with special enthusiasm and motivation, but when they played Newcastle it was like they had lost their spark a bit," he said.
"The result of the game does depend on some small things, though. For example, if they got a penalty for the handball against Newcastle, it could have been completely different."
|Coach: D. Moyes|
for A. Young 63'
for R. Giggs 63'
for A. Büttner 88'
|Emery wants new striker at PSG|
|Santos accept Juventus bid for Gabriel|
|Eriksson expects Sweden to try and tempt Ibrahimovic out of retirement|
|Spurs signing Janssen almost quit|
|Leicester stay best for Mahrez - Ranieri|
|Allardyce to take Mourinho cue on Rooney|
|Ings ready to outdo big-money signings|
|Henderson optimistic over Liverpool campaign|
|Allardyce hardened to the challenge of England post|
|Barcelona announce record revenues for 2015-16|
|Moyes enjoys Sunderland win as Palace beat Colchester|
|Stoke complete Allen signing|
|Roma coach Spalletti warns suitors off Manolas|
|Cresswell out for up to four months with knee injury|
|Burnley fan banned by club for racist abuse|
|Dad won´t let me play at the Olympics - Larsson Sr pulls rank|
|Kostic joins Hamburg on five-year deal|
|Tevez: I´d turn down Chelsea and Napoli to stay at Boca|
|Mayoral inspired by Benzema for Wolfsburg stint|
|Allardyce straight into competitive action with England|
|Liverpool, Sevilla fined for Europa League final incidents|
|Barcelona seal Guillemenot signing as part of new Servette deal|
|Niersbach handed one-year ban over World Cup corruption|
|Chelsea and Everton ´still interested´ as Koulibaly eyes Napoli exit|
|´Still working hard´ - Balotelli trains with Liverpool kids|
|Winter breaks, long-ball football and the World Cup: Allardyce in his own words|
|Inter warn Napoli Icardi is not for sale|
|Zanetti wants Simeone back at Inter|
|Stoke snap up Sobhi|
|PSG tougher under Emery - Lucas Moura|
|Totti not ready for retirement - Pallotta|
|Confident Allardyce reveals plan for England success|
|Pochettino to discard three Tottenham players|
|Allardyce: Rooney must wait for captaincy decision|
|Aubameyang: I will only leave Dortmund for Real Madrid|
|Allegri silences questions on Pogba|
|Bruce stands by decision to quit Hull City|
|Pochettino: Not the right time for Argentina job|
|Inter yet to approach De Boer with Mancini exit rumoured|
|Ancelotti trusts me more than Guardiola - Ribery|
|Wijnaldum rejected Everton for Klopp|
|Pre-season Manchester derby cancelled|
|Coutinho excited by ´fast´ Liverpool recruits|
|Cristiano Ronaldo and Conor McGregor step into the ring together|
|Mancini coy on reports linking Icardi to Napoli|
|Nolito reveals why he chose Man City over Barcelona|
|Inter 1 Paris Saint-Germain 3: Icardi absence in defeat fuels Napoli talk|
|MLS Review: Wright-Phillips double inspires Red Bulls to New York derby rout|
|James seeks more game time at Madrid|
|Rooney: I want to be a manager|
|Mignolet welcomes Karius challenge in Liverpool number one battle|
|Batshuayi buoyed by winning vibes at Chelsea|
|Moyes and Sunderland players diverted after plane fault|
|´Loved´ Varane targets long Madrid stay|
|Kostic set for Hamburg medical|
|Leicester crying over Kante sale - Ranieri|
|Schurrle the perfect Mkhitaryan replacement - Tuchel|
|West Ham face anxious wait on Cresswell injury|
|Mourinho will accept criticism from United legends|
|Bertolacci desperate for fresh start after underwhelming first season at Milan|
|Hoops hand Toure one-year deal|
|Origi ready to fight for Liverpool spot|
|Emery wants PSG stay for ´fantastic´ Matuidi|
|No Barcelona offer for Vietto - Cerezo|
|Burnley apologise for racist abuse from supporter|
|Guardiola will not rush Kompany comeback|
|Of course I´ll shake Guardiola´s hand, snaps riled Mourinho|
|Watzke: No more signings for Dortmund|
|Roma expect Manolas to snub Premier League move|
|Adriano set to leave Barcelona for Besiktas|
|Manchester United in worst possible situation - Mourinho|
|Sporting would have to sell stadium to afford Van Persie - Jesus|
|Jonas´ agent confirms Barcelona approach|
|No problem with Mourinho, insists Guardiola ahead of derby in China|
|Toronto´s hat-trick hero Giovinco: I´m back|
|Drogba revels in ´special night´, dedicates hat-trick to family|
|MLS Review: Hat-tricks for Drogba and Giovinco as stars shine|
|Whelan backs Liverpool for top-four finish|
|Pellegrini still waiting for right offer|
|Ronaldo deserves to win Ballon d´Or - Vazquez|
|Phelan wants Hull job|
|Alaba saddened by Gotze exit|
|Morgan: Vardy right to re-sign|
|Maradona ´hurting´ as Higuain closes on Juventus move|