Manchester United will lose more matches if they do not “grow up” and “start well”, says boss Jose Mourinho.
United rallied from 1-0 down to beat Juventus 2-1 on Wednesday – the fourth time they have come from behind to avoid defeat this season.
Mourinhos seventh-placed side face Premier League leaders Manchester City at Etihad Stadium on Sunday.
“If we keep conceding goals before the opponent, there will arrive the day where we cannot come back,” he said.
Manchester Uniteds Paul Pogba misses training to hand Jose Mourinho injury scare ahead of derby
United were 2-0 down to Newcastle in their Premier League match on 6 October but won 3-2. Two weeks later they conceded the first goal against Chelsea but fought back to draw 2-2.
Against Bournemouth last weekend, Marcus Rashfords 92nd-minute goal gave them a 2-1 win after conceding in the 11th minute.
In Turin on Wednesday, Cristiano Ronaldo put Juventus ahead but an 85th-minute free-kick from Juan Mata and an Alex Sandro own goal four minutes later saw United complete a famous Champions League comeback.
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“We are not a team that gives up,” said Mourinho. “We are a team that always finds a way to fight back.
“We have to make sure that we grow up, not just in our approach, because I think it is clear that the team is growing up, but we also have to grow up in our compactness and to start matches well.”
United could be bolstered by the return of Romelu Lukaku for Sundays derby, with the Belgium striker missing the Bournemouth and Juventus games because of injury.
“Lukaku is training with the team this morning,” said Mourinho. “If the answer is positive and we have, of course, one more session tomorrow, but if the answer is positive then he is ready.”
United finished second in the league last season – 19 points behind City. This season They are seventh, nine adrift of Pep Guardiolas side.
The last meeting between the sides in April saw United come from 2-0 down at half-time to win 3-2 and delay City clinching the title.
“We are going to try. I cannot say that we are going to be successful in our motivations and desires,” said the Portuguese.
“But we played two difficult matches away against two very good teams, Chelsea and Juventus, and we managed to get good results.
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“Even if the good results were not in our pockets, the performances were there. The positive attitude was there, so we are going to try.
“I dont think it [the Manchester derby] is special because of what happened last season. Its special because it is a Manchester derby and it means what it means.”
Mourinho and Guardiola worked together at Barcelona, as backroom staff and player respectively, but their relationship has been strained at times since turning to management.
But Guardiola said on Friday there is no problem between them: “We are both good guys, more than you expect. Its much better, believe me.”
The build-up to the derby has been overshadowed by German news magazine Der Spiegel alleging City – and PSG – overvalued sponsorship deals to help meet Uefas Financial Fair Play (FFP) rules.
“If the answer is positive and we have of course one more session tomorrow, if the answer is positive he’s ready but in this moment I can only say he trains with the team, I don’t know his answer.”
City said they will not be commenting on the claims and the attempt to damage their reputation is “organised and clear”.
Romelu Lukaku returns to Manchester United training ahead of derby
Guardiola said: “If they want to undermine us, no problem. We live our lives – we will remember in our hearts for the rest of our lives how we played.
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“If we have done something wrong we will be punished. The federation has to decide but I trust what the club tell me.”
The Belgian has missed recent games against Bournemouth and Juventus through injury, after also being dropped against former side Everton last month.
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“I understand how important it is but we played quite well [in Aprils defeat]. In the end we were champions. If we keep getting three points well be champions again.”
• Midfielder a doubt to face Manchester City on Sunday• Mourinho describes Citys football operation as untouchable
The midfielder has impressed for José Mourinhos side in recent matches, the World Cup winner a key factor in Uniteds uplift in form.
United and Pogba have won their last three matches, including Wednesday nights impressive 2-1 victory at Juventus but the Frenchman was unable to take part in full training on Friday. Instead Pogba undertook an indoors session at Uniteds training complex due to what is understood to be a small injury.
Mourinhos squad have a final session on Saturday before the trip to City so the manager will hope Pogba can take part before any decision about his availability for the match is taken.
The United manager, meanwhile, wants his side to take the fight to the Premier League leaders in the derby.
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Read more United are nine points behind City after 11 matches as they travel to the Etihad but they are enjoying a fine week, having won at Bournemouth and Juventus, while last month they drew at Chelsea after leading until the closing moments.
Mourinho, asked whether the wish was to go toe-to-toe with Pep Guardiolas team, said: We are going to try. I cannot say we are going to be successful in our motivations, in our desire, but we played two different matches away against two very good teams – Chelsea and Juventus – and we managed to get good results.
Read more And even if the good results were not in our pockets the performances were there, the positive attitude was there so we are going to try but Manchester City are a very powerful team.
Mourinho refused to be drawn on the alleged breaches of FFP rules by City but did praise their football operation.
It is difficult for me to answer because I focus on my job, I focus on the four lines [pitch], focus on football. If you want to speak about their football potential we can speak and football potential starts with investment, and after that of course there is a quality of the work, of the organisation – I think that is untouchable.
But what is behind I cannot say but in this moment I have only to think about football, and to think about football is to think about Manchester City as a football team there.
Romelu Lukaku could be available again following a hamstring injury. Mourinho said: Lukaku is training with the team this [Friday] morning. If his response is positive – and we have of course one more session tomorrow – he is ready.