Cristiano Ronaldo hopes to see Manchester United winning trophies again as the club continues to rebuild under Louis van Gaal.
Real Madrid forward Ronaldo won the Premier League three times, as well as the Champions League, FA Cup and three League Cups during a six-year spell at Old Trafford that ended in 2009 with a world-record £80 million move to the Bernabeu.
But United have not won any silverware since Sir Alex Ferguson retired on the back of a 13th Premier League success in the summer of 2013.
Speaking to the BBC ahead of the release of his film "Ronaldo" on Monday, he said: "For me it's hard to see that because it's a club that I love. Of course I want to see Manchester United at the level that it was in the past.
"Like, for example, Sporting Lisbon was my first professional club. I like to see the clubs that I like at the top and I think Manchester this season is better, but I think they still have work to do to be at the level of six, seven years ago."
Ronaldo has previously said he could one day see himself playing alongside United skipper Wayne Rooney again, while he did not rule out a return to United.
"Why not?" he told BT Sport. "In football, you never know what will happen tomorrow.
"People know I love Manchester United. It's great there -- they support me a lot."
The 30-year-old picked out several players who could one day reach the very top of the game.
"You see many players with potential," he said. "I will mention [Martin] Odegaard of Madrid for example, at 16 he's still young but you can see he's a very good player.
"[Chelsea's Eden] Hazard for example, the No. 7 of Manchester [United, Memphis] Depay is a good player too, [Juventus' Paul ] Pogba and maybe [Barcelona's] Neymar."