Seven-time World Champion Rossi is leading the Riders' Championship following his victory at Dutch TT with defending Champion Marquez 74 points adrift in fourth place.
While Marquez has had a difficult season to date with only one win and two podiums to his name, Saturday's victory at Assen was Rossi's third of the campaign while he has been on the rostrum in the other five races.
"First of all, I’m very happy for my [points] advantage over Marquez, for me – from now until the end of the season – he will become a big problem again," the Yamaha rider is quoted as saying by Motorsport.com
"My pace was not so bad, but I was not able to make a gap [to Marquez in the race]. Then, when I got quite tired, I made three mistakes, so Marc overtook me.
"It was good to understand his pace, because when I was behind him I could understand where I was faster than him."
Rossi moved ahead of team-mate Jorge Lorenzo in the standings with his latest win, but again he knows there is still a long way to go in the Championship.
"It’s like I cancelled Jerez or Mugello [where he finished third each time], because Jorge recovered nine points over me, and this time I was able to come back and recover another nine to him," he added.
"And now I lead [Lorenzo] by 10 points, but I know it will be a very long, and very difficult Championship."