New boss Erik ten Hag and his United squad continue their preparations as they kick off their new season at Old Trafford on Sunday. The 37-year-old, who wants to leave United just a year after his impressive return from Juventus, was among the squad being paced by the Dutchman. Cristiano Ronaldo pictured in training with his Manchester United teammates The 37-year-old unheralded star was among United’s pace-setting squad Ronaldo was caught in action on Thursday at the Red Devils’ Carrington training base and boss Ten Haag has a big decision on his hands. The Dutchman may have to start Ronaldo despite a lack of pre-season training with fellow midfielder Anthony Martial reportedly set to miss the season opener through injury, according to The Athletic. The Frenchman, who scored three goals on the tour, has been dealing with a minor hamstring problem and the timing of his return is unclear. Anthony Martial is set to miss the opening game of the season against Brighton Whether he starts or not, Ronaldo still hopes to leave Old Trafford in the coming weeks. The former Real Madrid star has had a pre-season disruption as he did not travel with the rest of the squad on their pre-season tour of Thailand and Australia due to family reasons. Instead, he stayed in Portugal and trained alone. Bayern Munich, Chelsea and Atletico Madrid have been linked with a summer move for Ronaldo, but all three clubs have distanced themselves from those reports. The forward was arrested in action on Thursday at the Red Devils’ training base in Carrington United have so far maintained that Portuguese forward Ronaldo is not for sale this summer It appears that the forward’s agent, Jorge Mendes, has informed United of an offer and wants the Red Devils to quote their price. United have so far maintained they are not for sale, with the former Real Madrid man still having a year left on his contract. It is also Ronaldo’s first training session since being heavily criticized by coach Erik ten Haag. The Dutchman branded the forward’s behavior “unacceptable” after he left Old Trafford before the end of Sunday’s 1-1 draw against Rayo Vallecano in a pre-season friendly. The Portugal international took off at half-time and then walked off the pitch 10 minutes before full-time without his manager’s permission. Cristiano Ronaldo left Manchester United’s friendly with Rayo Vallecano in the early hours of Sunday Despite suggestions that United had no problem with Ronaldo’s early departure, Ten Haag criticized the player’s behavior in an interview on Dutch television. Asked if he condoned it, United’s new boss said: “Absolutely not – it’s unacceptable for everyone. “There were many more who went home. I tell them that it is unacceptable and that we are a team and that we must stay until the end.’ Manager Erik ten Hag (left) described the star’s decision to leave early as ‘unacceptable’ The former Ajax boss, however, says the five-time Ballon d’Or winner is part of his plans – but he still has to prove he is a top player. “I think it can,” he told Sky Sports. “But to start he has to be fit, he’s just started. “He is a fantastic footballer, he proved it so many times, but you can always be judged by what you are now, what you present now, what you perform now. So the team and Cristiano himself have to prove it. Meanwhile, former United manager Chris Armas has urged Ten Haag to take a hands-on approach to ensure Ronaldo stays at Old Trafford. Armas served as Ralf Rangnick’s assistant during the German’s six-month stint as interim coach last season. The American said: “He’s a big part of the team and he’s still a guy who’s been producing so it would be my job to figure out how to take all that talent and all that fire and experience of winning and challenge him as much as possible I could. . Former United manager Chris Armas (pictured, left) has urged Ten Haag to take a hands-on approach to ensure Ronaldo stays at Old Trafford “I think the most important thing is to deal with Cristiano. He has so much to give, again his commitment to winning and scoring. “Each guy has his different type of leadership – he can definitely be a leader in his own way and my goal like everyone on the roster was ‘how can I get the best out of Cristiano?’ “So I think it’s a hands-on approach, it’s talking to him, bringing him into the office, asking him questions. So it is part of the solutions and part of the success.’