Alex Ferguson says Manchester United manager Jose Mourinho can rival Pep Guardiola, even though he rates Manchester City as Premier League title favourites.
United defeated rivals City 1-0 in the EFL Cup on Wednesday, although they already trail their rivals by six points in the Premier League and lost at home to them in the top-flight last month.
Former Old Trafford boss Ferguson, who has said he rates City "as favourites from five potential candidates" in the title race, believes Guardiola cannot be questioned despite his side's six-match winless run.
But he is confident Mourinho has the skillset to challenge the Catalan throughout his spell in England, despite making a mixed start to his United career having been sacked by Chelsea last season.
"Guardiola's skills are beyond debate, [Antonio] Conte is getting Chelsea on track, but Mourinho can also rival Guardiola," Ferguson said to Kicker.
"He has won the Champions League with two different clubs and titles in three different countries.
"The rivalry and the experience of Guardiola and Mourinho make for an exciting competition."
Even though he admires the City manager, Ferguson feels United's rivals performed very poorly in their 4-0 Champions League defeat to Barcelona and thinks Guardiola missed a great opportunity to defeat his former club.
The United legend warned City they are far from certain of making the knockout stages following the defeat.
Ferguson said: "I was a bit disappointed with Manchester City because Barcelona were not overwhelming in their 4-0 win.
"Sure, whenever Lionel Messi sees a chance he converts it, but the overall system of play wasn't outstanding. City missed a good opportunity there.
"Because Monchengladbach, even without several starters, put in a convincing performance at Celtic and got a victory they really deserved.
"City still have a big job to reach the knockout stages."