Drew Seeley believes Vanessa Hudgens resented him on the High School Musical Tour because she wanted to sing with Zac Efron
Seeley replaced Efron on the concert tour based on the hit Disney Channel Original Movie.

Vanessa Hudgens may have been missing then-boyfriend Zac Efron on the High School Musical concert tour, according to Drew Seeley.
On a recent episode of Will Friedle and Sabrina Bryan’s Disney Channel Original Movie re-watch podcast Magical Rewind,

Seeley opened up about joining the High School Musical cast for High School Musical: The Concert, which played 51 dates across the U.S., Canada and Latin America in 2006 and 2007.
Seeley famously recorded vocals for Efron’s HSM character, Troy Bolton, which were reportedly blended with Efron’s in the hit 2006 Disney Channel movie.

“I was never told why they did it the way that they did it,” Seeley told Friedle and Bryan. “But I think that they were within about three, four weeks of shooting the actual film, and they had me and not Zac.
Me and the rest of the movie cast all go into the studio for, like, four days straight and record all the songs together. So, yeah, I knew that I was doing that.”