The 20-year-old has been involved in all but one of United matches this season – missing the defeat to Newcastle United through injury – making 37 appearances in all competition and scoring 10 goals.
Already competing for a place alongside Jesse Lingard, Romelu Lukaku and Anthony Martial, the arrival of Alexis Sanchez has shifted Rashford down the pecking order.
In fact, Rashford has not been named in a top flight starting eleven since the Boxing Day draw with Burnley and Henry believes the versatile forward will assess his role at Old Trafford in the summer.
"One of the most important things for me is that you have to play," Henry said on Sky Sports, according to Sports Illustrated.
"You cannot be on the bench and missing games, missing learning about the game and stopping that momentum, and an example is Rashford.
"Michael Owen had the opportunity to back up what he did the year before because he played, and he played, and he played, and he played – and I can give you more examples.
"But Rashford at times could not capitalise on what he did from that year [after his debut], because sometimes he is playing on the right, [sometimes] on the left.
"Leave is a strong word. Obviously being from there, he wants to play for United. But he has to play and it is becoming even more difficult for him since Sanchez has arrived. I think at the end of the season, he is maybe going to have a thinking day of 'do I stay?'"
Rashford will be hoping to return to fitness in time for United's next game against Huddersfield Town in the FA Cup, a competition he has been a regular in this season.
An undisclosed muscle injury kept Rashford from featuring for United at St James' Park last Sunday (11 February), with manager Jose Mourinho coy regarding the timeline for his return.
Despite tumbling down the pecking order Rashford is still expected to play a central role in Gareth Southgate's England squad for the World Cup in the summer.