In a social media Q&A, the 22-year-old was asked about his partnership with he French forward, and why Martial might have struggled under the leadership of Mourinho.
Rashford said of his link with Martial: “I think initially when I first came into the team it was good, we had a good connection on the pitch.
“That few months I had with Louis van Gaal, it was 100 per cent enjoyable to play with him and we were playing well together.
“But then after that the situation with the manager changed and it ended up nine times out of 10 it was one or the other playing."
Van Gaal left the club in May of 2016 despite leading them to an FA Cup triumph over Crystal Palace at Wembley.
Rashford has now suggested that his departure was a bad thing for his partnership with Martial, with the pair now both regular starters under Solskjaer.
He continued: “We didn't really get to play together for that season, it was a bit of a difficult period not to play with him because I enjoyed playing with him on the pitch.
“This season we've definitely shown we can play together and play well together."