The former Albiceleste physio is certain that the Blaugrana star will be better than ever from the 2012-13 campaign onwards as his development reaches the final stages
Signorini worked with Diego Maradona ahead of the 1986 World Cup, and was also part of the Argentina staff when the Napoli legend was in charge of the national team from 2008 until 2010.
Despite Messi having already amassed numerous titles, records and accolades including three successive Ballon d'Or honours, Signorini feels that the 25-year-old has not even entered his best phase yet.
"Leo will reach his peak this year, starting this season. Regardless of everything that he has already achieved, he will now start to write history. His best is yet to come," Signorini was quoted as saying by Sport.
"Up till now, everything he has done was the result of his intuition and his desire to play. However, from now on the element of preparation will come into the equation as well. His choices will no longer be just based on his instincts, but also on his knowledge and experience.
"He will enter a new stage of his game. It's impossible to say where his limits lie. It's a mystery what he can achieve. Players like him are very rare."
Messi netted 73 goals in all competitions for Barcelona in 2011-12, including a record-breaking 50 in La Liga to claim the Pichichi trophy.