Felipe Massa considers his former Ferrari teammate Fernando Alonso to be "on the same level" as Michael Schumacher but saw his Formula 1 career impacted by one negative trait.

This week, the double world champion confirmed he will be leaving the grid at the end of 2018 and is likely to race in IndyCar as part of his bid to win the Indianapolis 500 and complete the 'Triple Crown'.

A return to F1 in 2020 hasn't been ruled out, however, just prior to his big announcement, the Brazilian, who many considered his No.2 during their stint together at Maranello, was full of praise for the Spaniard.

"As for pure talent, I would put Michael and Fernando on the same level," Massa said, having also driven alongside the great German at Ferrari in 2006.

"Alonso has the gift, the ease, of understanding a race and driving incredibly fast. A highly intelligent driver with extensive skills and I would say all that also about Michael."

If the 37-year-old doesn't come back, however, his legacy will be one of a possible all-time great who's achievements in F1 fall well short of what they could have been and for Massa, who himself retired at the end of 2017, that is down to one reason.

"Outside of the race car, I had zero problems with Alonso, we have always maintained a healthy working relationship," he explained.

"With Fernando, that’s one thing. If he pulls down his visor, he becomes another person. He can split a team. We saw that in many racing teams he drove for.

"I see that as his problem. Maybe he could have made more of his talent without this trait."

Certainly, his explosive season with McLaren in 2007 alongside Lewis Hamilton defined much of Alonso's career, with the infamous 'Fernando is faster than you' incident with Massa at Hockenheim in 2010 another, in what was their first season together at Ferrari.

The superiority of Red Bull and then Mercedes ultimately put pay to his hopes of a third world title and in today's F1 driver market, despite his undoubted speed, no top team would risk having him in one of their seats as the stigma of 2007 continues to haunt him.

That's why, as much as the sport will miss him, calling time on his 17-year stint was ultimately the only decision for a man still driving at his highest level.