The duo helped Fabian Hurzeler's men secure all three points on Sunday as they came from a goal down to beat Manchester City on Sunday at the Amex.
Following the 2-1 victory, head coach Hurzeler said having Milner on the pitch is like having a "second coach" and hailed his "special mentality".
And now, 21-year-old Gruda has talked up the importance of having the 39-year-old around the Sussex side.
When asked about the importance of having Milner as a team-mate, he said: "Yeah, I think I'm the right person for this question.
"I think every day in training, when I'm training, he pushes me 100 per cent, every day, every minute. If I do something wrong, I know it, because I have James Milner in my back and he tells me this every time.
"I think this is the most important for me. He helps me a lot. If I do something good, he helps me. If I do something wrong, he helps me. I'm very happy to have him in the team, and I'm looking up to him."
Hurzeler was equally effusive in his praise of Gruda as he was for ex-Liverpool star Milner. The German described his fellow countryman as someone who can be a "game changer for every team in the world".
Both Milner and Gruda will hope Hurzeler's compliments pave the way for more game time away at Bournemouth on September 13 when the Premier League returns.