The Arsenal forward was speaking to the media ahead of Brazil's third group game against Scotland, with the Barcelona winger's World Cup participation uncertain after he was withdrawn in the 40th minute of the 3-0 win over Haiti.
Martinelli acknowledged the squad's concern but insisted Brazil's attacking depth remains significant.
"We are sad for what happened to Rafa," he said. "But Brazil has a lot of quality players. I prefer to play on the left, but many times at Arsenal I have played on the right.
"I also did it against France in the friendly here in the United States. The decision is the manager's."
On Neymar, who has yet to feature for Brazil during the tournament as he continues working his way back to fitness, Martinelli was enthusiastic.
"He is at a very high level. We see his quality. Everyone knows his quality. The intensity with which he has returned shows how much it means to him. And having a player like him available is fantastic."
Martinelli also reflected on the contrasting styles of Ancelotti at international level and Mikel Arteta at Arsenal.
"They are very different, the styles of the two. I have to change when I arrive here. They are two great coaches and I am very happy and honoured to work with them."
Asked about the prospect of forming an attacking partnership with VinĂcius JĂșnior, Martinelli was predictably enthusiastic: "Every player in the world would be happy to play alongside Vini."