The 27-year-old secured a shock loan move to Barcelona during the summer transfer window, with the La Liga champions having a reported £30 million option to buy at the end of the season.
Should they decide to activate that option, it would end a 20-year relationship between Rashford, who joined Man United’s academy at the age of seven, and the club.
Rashford has made an instant impact at Barcelona, already scoring five goals and providing five assists in his 13 appearances across all competitions.
Former Man United forward Saha believes Rashford should have tried to find a solution with the Premier League side, however.
"As a professional, you need to find solutions, regardless of whether the manager likes you," Saha said, speaking to football betting site BetVictor.
"We all face moments where we have to perform on the field, and that wasn't his response. There were definitely times I saw a player who was out of form, who didn't want to be there, and that's not normal.
"It's not normal to play like that. You might want to request a transfer, but when you're on the field, you work hard. He wasn't working hard, something was clearly wrong, and he was unhappy.
“You shouldn't let anything take away your joy on the pitch because you have a responsibility to your fans. It's not about the manager, or the club owners; it's about the thousands of people paying for tickets.
"I get angry because it feels like a waste, and it shows a lack of accountability. Now, I'm very happy for him as a football player, not just for me, but for fans all over the world in Barcelona who can now enjoy a terrific player. But, of course, as a Manchester United fan, I'm angry."