"This is good preparation for us because it is important that my players get games before we play a Champions League qualifier.
"It was especially pleasing to see Rossi and Dong score the goals because they both have the potential to come through.
"We've had Rossi a year now and he's coming on nicely. He has the ability to take his time in front of goal. It was a typical goalscorer's goal. It bounced off his belly, I think, but he was there to meet it.
"A lot of goalscorers in the game score goals like that; you think of Gary Lineker, that type of player. He's got great potential, the boy."
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"Now we go to China and Japan and I aim to give everyone as much playing time as possible."
"That was an important step for him (Dong), he has potential and now we need to get him a work permit so we can get him into England and push his development," said Ferguson.
"At the moment that's been spasmodic because he's been at Royal Antwerp in Belgium then going back to China, so the continuity hasn't been good.
"But I was pleasantly surprised considering that was his first-team debut and he showed a good turn of speed and composure for his goal."
United won 2-0 with goals from Rossi and Dong. RVN was lucky to remain on the pitch after losing his temper with one Hong Kong player and missed loads of chances.
Rio may also be considering playing in Hong Kong full time after getting a break from all the hassle.