It was at Turffontein Racecourse in Johannesburg, back in the summer of 2006, that Sir Alex Ferguson allowed his mask to slip on the thorny issue of Jose Mourinho's Chelsea.

Speaking at a private event during Manchester United's preseason tour of South Africa, Ferguson claimed that Chelsea, which had just won the Premier League title for a second successive season, were "hell-bent on ruining football" and that there was "no way" his club could match the unfettered spending power of Stamford Bridge owner Roman Abramovich.

Rather than despair about the situation facing his team, Ferguson used it as motivation, and 12 months later, United were champions again, with emerging players such as Wayne Rooney and Cristiano Ronaldo at the fore of a new era of domination that saw the club win three consecutive titles and the Champions League.

Mourinho and Chelsea looked set to dominate for a decade, thanks to Abramovich's money, and Ferguson was in danger of becoming yesterday's man, but his achievement in halting the Chelsea juggernaut and restoring United to the summit of the game was as great as any of his previous successes at Old Trafford. Fast-forward to the present, and Mourinho is facing a similar career crossroad as United manager, which is why his decision to commit to a new contract at the club is so significant.

Sources have told ESPN FC that United and Mourinho are waiting for the right moment to confirm his extended deal, but the fact that he sees his future at Old Trafford suggests that he is ready to tackle his career-defining challenge in the way Ferguson met his.

Mourinho's task is to find a way to get the better of Pep Guardiola and Manchester City, and the outcome of his personal battle will define his career. If he pulls it off, Mourinho will be the guy who proved his ability to stick around and rebuild a club at the same time as toppling a fearsome rival, as Ferguson did to him and Chelsea. But if he falls short, either by failing to meet the objective or walking away from United with the job half-finished, it will draw a line under his time as an elite coach. It will be seen as a challenge too far, and Mourinho will be washed away by the new wave of coaches emerging, just as he did to the old guard as the braggadocio Porto manager back almost 15 years ago.

Mourinho's problem is that he is regarded as a coach who does not last the course. He did three years in his first spell at Chelsea and the same at Real Madrid, but he will have to remain at Old Trafford much longer than that if he is to genuinely put United back on top. Guardiola has put City so far ahead of the pack this season that it is difficult to envisage anything but them being the team to beat next year. Therefore, Mourinho needs to be in it for the long haul.

Mourinho doesn't usually linger at any one club, but his extension at Man United suggests that he is ready for a long-term challenge. Matthew Peters/Man Utd via Getty Images

United's audacious move for Alexis Sanchez, when the Arsenal forward appeared destined for the Etihad, is a good start, and it shows that Mourinho still has the fight within him. He will expect more money this summer, too, and it is unlikely that he will have agreed to a new deal without promises of a big push in the transfer market, but Ferguson did not topple Chelsea by out-spending them, and his former assistant manager, Mike Phelan, has told ESPN FC that money alone will not be enough to catch City.

"Even when Chelsea were so dominant, Sir Alex's basic principle was that we [United] would only get back to the top by focusing on being the best we could be," Phelan said. "He always believed it was just a case of time and working in the right manner to win again.

"There were players that we were keen on, such as Arjen Robben and Michael Essien, whom Chelsea were able to sign because of their spending power, but Sir Alex never panicked or spoke about Chelsea being uncatchable.

"We just stuck to our principles, but the difference now is that time is in much shorter supply for clubs and managers. The challenge facing Jose is very similar to that which Sir Alex had to contend with, but he also needs time to put a plan in place and follow it through."

Where Ferguson had Rooney and Ronaldo, plus the old heads of Ryan Giggs and Paul Scholes and ready-made stars such as Carlos Tevez, Mourinho has the likes of Paul Pogba, Anthony Martial and Marcus Rashford as his young generation, with Romelu Lukaku and (sooner rather than later) Sanchez to add potency to United's strike-force.

A Mourinho team is beginning to take shape, but it is still in the building phase, unlike Guardiola's at City. If Mourinho is around to sign another new contract in two or three years' time, though, he is likely to be much closer to achieving his objective ... if he hasn't already pulled it off by then.