Rooney, who held that same title after United paid £27m for him in 2004, had to ask Old Trafford colleague Bastian Schweinsteiger who Martial was as the uncapped French forward neared a £36m move from Monaco.
“It is normal that Wayne Rooney doesn’t know me,” said the 19-year-old. “I have played a lot in Ligue 1 but I’m happy to go there, he is a big player and next to him I will improve my game a lot.”
Martial can play across the front three but hopes, after talks with United manager Louis van Gaal, to be used as a striker despite having just 15 goals to his name in senior football.
“He asked me my preferred position. I prefer to play in the centre but he told me I could play in a number of positions,” he added. “The coach decides but whatever position I play, I will do the best I can.”
Midfielder Juan Mata, meanwhile, has backed Spain team-mate David de Gea to overcome the turmoil of his collapsed move to Real Madrid and win over United fans again.
“It’s been a manic few days for him,” said Mata of De Gea, who has been named in United’s Champions League squad.
“His personality will help him. He manages to play even better in moments of maximum pressure and stress. His hunger and professionalism are intact. We all know what a great goalkeeper he is and he would make any team in the world better. The fans will get behind him and so will the team.”