Vandoorne has been a member of McLaren’s Young Driver Programme for just over three years and last season secured the GP2 championship in some style, scoring seven wins en route to the title.
However, with Fernando Alonso and Jenson Button signed for 2016, there was no space to promote Vandoorne to a race drive, no matter how highly the team rate him.
“He has always been intelligent, but to that intelligence he has recently added a level of wisdom unusual in one so young,” Dennis told F1.com when asked about the 23-year-old Belgian.
“And he is as physically fit as any racing driver in any race series in the world, including Formula One.”
This season Vandoorne will race in the Super Formula series in Japan, as part of Honda-powered Docomo Team Dandelion Racing, and Dennis expects more success from his team’s protege.
“Super Formula cars are fast and grippy, and Stoffel will be competing against ex-Formula One drivers such as Kamui Kobayashi, Kazuki Nakajima, Narain Karthikeyan and Andre Lotterer. He will fare well.
“His journey to Formula One has been mapped out very carefully, as is always the case with McLaren Young Driver Programme members, and we expect him to be ready in 2017.”
However, Dennis refused to be drawn on the chances of there being a race vacancy with the Woking squad next season, stressing only that he is more than happy with their current line-up of Fernando Alonso and Jenson Button.
“Fernando has repeatedly confirmed that he intends to complete the three years of his current contract,” he stated. “And that contract contains no options or performance clauses by the way: it is three years straight.
“As for Jenson, he and I will speak during the course of the year. But he is a world champion, and one of the very best drivers we have ever had. Any team would be delighted to have him on their driving strength. We most definitely are.”
Check back to Formula1.com on Wednesday to read the exclusive Q&A with Ron Dennis - during which he discusses McLaren's 2016 prospects and the ongoing partnership with Honda - in full.