The 21-year-old was tipped to lead the line for United this season following the departures of Romelu Lukaku and Alexis Sanchez but he has tended to play from the left with Anthony Martial preferred through the middle.
Rashford scored twice during Uniteds 4-0 win over Chelsea on the opening day of the season, but he has failed to find the target in four matches since for both club and country.
Southgate stated that Rashfords hold-up play isnt as effective as his strike partner Harry Kane and instead considers him as more of a wide raider who can cause damage when floating in off the flank.
When asked whether Rashford is inspired by Kane, Southgate replied: Theres a little bit of that.
But also, a little bit, that although weve for a long time almost wanted Marcus to be that option as a nine, Im still not certain that that is where he is happiest and where he does his best work.
A lot of his development at United was as a wide raider and I think he isnt as strong as Harry with his back to goal and holding play up, so if he plays as a nine, he will play it differently to Harry, but a lot of his best work is in that inside-left channel coming in off the line.
I dont think thats a problem, we just have to be aware that thats probably his profile to get the best out of him, theyre the areas on the pitch that he needs to get in.