The 21-year-old had a successful debut season when he joined the club from Monaco in the 2015/16 season, scoring 17 goals in his first year.
However, his future has been in doubt following a disappointing second season in 2016/17 where he found limited game time under Jose Mourinho, both up front and on the flanks.
Martial started United's season opener against West Ham United on the bench as well, but came on to score the Red Devils' third goal of the game, celebrating in a subdued manner.
Having recently been linked with a move to Inter Milan and Tottenham Hotspur in what is a World Cup year, Petit was said that his fellow compatriot is better off at United as he will get more chances to impress this year.
"Manchester United, they are building a team to play for the title this year," Petit told SFR Sport, as quoted on The Mirror. "They will play the Champions League, he [Martial] will have playing time and the competitions will be long until the end of the year."
"So going to Inter which is under reconstruction, there are a lot of uncertainties at this level there. It's a risk to take but I think he has the qualities to claim to play more at Manchester United.
"Whether it is on the left side or even in the centre, he has already shown that he has the instinct of a scorer."
The former Monaco player scored just eight times in 42 appearances in all competitions last season and has a total of 26 goals in 92 games for the club.