Rashford scored his first goal of the season in the 3-2 win.
Solskjaer revealed: "He was getting better and better. I had a little bit of a go at him halfway through the first-half for a tackle he evaded, but I think his reaction, his sharpness is getting better, he's more direct.
“You can see his confidence is getting there. Great goal and great run - and great finish for the one that was disallowed as well. And I think Marcus will really kick on this season.
“I'm very happy for Marcus to get that goal. He was just a couple of inches offside on a counter-attack we had, with a great cross from Mason [Greenwood]."