Cristiano Ronaldo spent just 26 minutes on the pitch against Chelsea during Michael Carrick's second game in charge at Manchester United. However, many pundits feel justified in Carrick's decision to keep Ronaldo on the bench. They believe the legendary forward is an incredible goalscorer but he cannot blend well with Carrick's high-press tactics.On many occasions this season, Ronaldo has maintained a solitary position in attack. He has focused on scoring the necessary goals but hardly chased down opponents. Many fans believe the striker should be left to focus on his goalscoring prowess. Some pundits, however, and Carrick clearly expect him to play to energy-draining first-line-of-defense tactics as well.Clearly, Cristiano Ronaldo won't be a big fan of Michael Carrick's management, especially with the star failing to start against Chelsea. With Ralf Rangnick potentially using similar tactics, chances are the Portuguese maestro might have a progressively difficult season at Old Trafford.However, the legendary striker has studiously played under many brilliant managers who got the best out of him. While Cristiano Ronaldo struggles to provide impact within tactics he isn't suited to, let's take a look at some of the best managers who have coached him.#5 Fernando Santos | Portugal national teamPortugal v Spain - International FriendlyThe Portuguese manager is popular for guiding Seleccao to a dramatic win at the European Championship in 2016. He also won the Nations League trophy in 2019. However, many aren't familiar with Fernando Santos' history with the Portuguese club Sporting. The then Sporting manager notably played Cristiano Ronaldo against Manchester United, which led to the star's move in 2003.The CR7 Timeline.@TimelineCR7FERNANDO SANTOS:"Cristiano Ronaldo is part of the team as always, he's captain of the team, and for him it's always an extra motivation to play for the national team."6:56 AM · Sep 1, 20212231140FERNANDO SANTOS:"Cristiano Ronaldo is part of the team as always, he's captain of the team, and for him it's always an extra motivation to play for the national team." https://t.co/cbjyKp0cgOThe duo were reunited in 2014 when Santos was appointed as the manager of the Portugal national team. Together, Santos and Ronaldo have won two important trophies with Seleccao. Cristiano Ronaldo has enjoyed Santos' reign in Portugal's camp. The star finally picked up his first major international trophy under Fernando Santos.#4 Carlo Ancelotti | Real MadridAthletic Club v Real Madrid CF - La LigaIt was a short stint with Cristiano Ronaldo as Carlo Ancelotti managed Real Madrid for just two seasons. However, their partnership was essential to the Portuguese maestro's growth. Ancelotti notably pushed Cristiano Ronaldo into playing as an all-out striker, rather than sitting in his comfort zone on the wing.TCR.@TeamCRonaldoCarlo Ancelotti: “I think Cristiano Ronaldo should always WIN the Ballon d’Or. He is the best I’ve managed and seen.”10:02 AM · Mar 4, 20205096606Carlo Ancelotti: “I think Cristiano Ronaldo should always WIN the Ballon d’Or. He is the best I’ve managed and seen.” https://t.co/Fc2s6LcqdbAncelotti guided Los Galacticos to their first-ever Club World Cup title in 2014. He also ended Real Madrid's 12-year drought for the UEFA Champions League, winning 'La Decima' in 2014. Under the Italian tactical genius, Ronaldo scored an astonishing 112 goals in just 101 games. He set the world alight with his brilliant performances.