After 27 seasons, legendary Manchester United manager Sir Alex Ferguson has decided to step down, leaving arguably the greatest legacy of any manager in club history.

Ferguson won 38 trophies, including 13 Premier League titles and two Champions League titles. No Premier League manager has ever come close to duplicating this success.

Ferguson, 71, has been involved in professional football since 1957 without a year off. He retired as a player in 1974 with Ayr United, after stints with Queen’s Park, St. Johnstone, Dunfermline Athletic, Glasgow Rangers, and Kalkirk. Immediately after retirement, he managed East Stirlingshire for one season, before taking on St. Mirren, Aberdeen, and then the Scotland national team.

The Scotsman was appointed Manchester United’s manager in 1986. He became more of a disciplinarian when he joined the club, as players were perceived to be out of shape and not fully committed to success on the pitch.

His first brush with success with United came in 1989-1990, when the club won the FA Cup. A Premier League title followed in 1992-1993.

Manchester United would retain several star players for an extended period of time under Ferguson. Ryan Giggs, Paul Scholes, Rio Ferdinand, Gary Neville, Roy Keane, and David Beckham are just a short list of players who spent a large portion of their prestigious careers at Old Trafford, which strengthened the club’s consistency both domestically and in Europe.

Ferguson would go on to win 10 Premier League Manager of the Season awards, as well as UEFA Manager of the Year in 1999. It was in that 1998-1999 season that Ferguson helped guide the Red Devils to the treble: a Premier League title, an FA Cup title, and a Champions League title. In that same year, he was knighted.

The question now for Manchester United is, who will replace him? There are two notable candidates that have immediately emerged: Real Madrid manager Jose Mourinho and Everton manager David Moyes.

Mourinho, who has two Champions League titles to his credit, has been regarded as perhaps the best manager in the world in recent years. The former Chelsea manager has long been rumored to be interested in a return to England, and has previously been considered the likely successor to Ferguson.

In recent months, Mourinho has given veiled hints that he would like to manage in the Premier League again. He has frequently expressed his admiration for the English style of play, and he and Ferguson are considered close friends.

Since leaving Porto for Chelsea in 2004, “The Special One” has received considerable media attention for his success with Inter and Real Madrid. His next club would likely need the payroll that he believes would garner him immediate success, and Manchester United fit that description.

In recent months, Real Madrid star Cristiano Ronaldo has been linked with a return to Old Trafford in a transfer that could exceed £100 million. There has been speculation that both Ronaldo and Mourinho would leave Madrid for Manchester.

Moyes, a 50-year-old Scotsman, was a journeyman as a player, and said on several occasions that during his playing career he was already taking notes on how to manage a club. His first manager position was with Preston North End in 1998. He lifted the Lilywhites from near relegation to the Division Two playoffs in less than two years.

Moyes’s contract with Everton is up after this season, and he has reportedly put off an extension in an effort to keep his options open. That also helps United avoid any compensation to Everton.

Considered a disciplinarian like Ferguson, Moyes has made the most with far less resources during his 11 years with Everton. He led the Toffees to a top four finish in 2005, and a runner-up in the 2009 FA Cup. Moyes also won the LMA Manager of the Year award three times, and signed current United striker Wayne Rooney to his first professional contract.

Many reports have pegged Moyes as the odds-on favorite to succeed Ferguson, who called him a “first-class” manager earlier this season. The Independent said the Red Devils hope to have a contract worked out with Moyes by the end of the week.