- Park Ji-sung won four league titles at Man Utd
- South Korean played for the club from 2005-2012
- He was first Asian player to captain Man Utd
(CNN)By Manchester United's high standards, it has been a difficult four years.
True, last season United might have won three cups -- the Community Shield, the Europa League and the League Cup -- but England's most successful club has not won a Premier League title since 2013.
That was the year Alex Ferguson -- their distinguished former manager and British football's most successful boss -- retired.
The post-Ferguson years have been ones of upheaval and change -- historic defeats under the Scotsman's initial successor David Moyes, then disenchantment at the turgid football of Louis van Gaal's team.
Now under current boss Jose Mourinho there is hope, says former player Park Ji-sung, that the club can once again become a force in the English Premier League and Europe.
"We're almost through that dark tunnel," Park tells CNN Sport, adding that Ferguson was a huge influence on his career.
"After Sir Alex Ferguson it's been a difficult time for Man United, but actually many people knows that after Sir Alex Ferguson it would be difficult time for Man United. Now you can see this season the performance is great. Hopefully it will be the same as under Sir Alex Ferguson."
'Premier League not a two-horse race'
The Champions League winner, a former midfielder famed for his endless energy, won four league titles at United and was the first Asian player to captain the club and play in a Champions League final.
Adored in his home country, Park has also played 100 times for South Korea, scoring at three World Cups. He is widely regarded as Asia's most successful footballer.
Park said he hoped Mourinho, who was appointed United boss on a three-year deal in May 2016, could continue his feat of winning a league title in his second season at every club he has managed.
"Particularly this season, they are doing so well under Mourinho," said Park.
Though United won those three trophies in Mourinho's first term, they finished a disappointing sixth in the league.
But Mourinho's men -- boosted by the summer acquisitions of Romelu Lukaku and Nemanja Matic -- are currently in fine form, jointly leading the Premier League after an unbeaten start.
"He knows more about Man United now," added Park of the former Chelsea and Real Madrid boss.
"His second season is always good. In his first season, he knows what the club wanted. He found some things, brought in some players who he wanted and now it looks strong."
United and Pep Guardiola's Manchester City are the league's in-form teams, with both winning six and drawing one of their opening seven games, but Park warned against expecting a two-horse race this season.
"I know this moment it's two clubs [City and United] that really fight each other, but the season's long and I know Chelsea, Arsenal and Liverpool all compete during the season.
"Always the Premier League has several clubs fighting for the title.
"At the moment, it looks like two clubs. We need to show our quality and don't think about other clubs, like Man City.
"The season's long, just focus on what they [United] have done because they've done so well and if we can continue with that then I think we can win the title again."
The excitement of United v Liverpool
Arguably, United's first real test in the league this season will come on Saturday when they travel to Anfield to face Liverpool, who have won only one of their last seven games.
England's two most successful clubs are fierce rivals -- former Manchester United defender Gary Neville once described the fixture as a "blood feud that's Sicilian in intensity."
Park admitted that United versus Liverpool was a match the players, as well as the fans, get excited about.
"Because of the history and the fans and the players, everyone involved in these matches knows that feeling and wants to win the game," he said.
"That makes it a different atmosphere at the club as well. Players know the feeling is different and the media focus on that and fans are excited about the match. It's pretty fantastic with everything happening before the matches.
"Now this period of time they [Liverpool] are struggling, but probably they want to get a turning point against Man United ... We need to prepare well to beat Liverpool."