Rossi continued as a reserve driver into 2015 for the newly formed Manor Marussia F1 Team. He finally made his debut at the Singapore Grand Prix. Rossi chose No. 53 as his career car number in honor of Herbie; his original choice was No. 16, which he used in his karting career, but the number was already claimed as a reserve number by Red Bull Racing. Rossi qualified 20th and last for his debut, but rallied to finish 14th, just ahead of teammate Will Stevens (15th), despite losing radio communication with his crew around the halfway point of the Grand Prix. Rossi would go on to enter five of the final seven races of the 2015 season. At the Japanese Grand Prix, Rossi finished 18th, again one place above Stevens. He would go on to equal Manor Marussia's best result of the season at his home race, the United States Grand Prix, finishing 12th, and becoming the first American driver to race at a track purpose-built for Formula One in the United States. Rossi then took 15th at the Mexican Grand Prix before completing his five-race stint at the Brazilian Grand Prix with a 19th-place finish.