Why Felipe Massa chose the right time to retire from Formula 1

Williams has enjoyed a competitive revival in F1 since Massa joined in 2014, and the team is quick to credit the Brazilian for the integral part he's played in that.

Both entities were perfect for each other back then. Williams needed a driver with top-team experience to help drag it out of a competitive slump; Massa needed a place to rebuild his reputation after a tough end to his stint at Ferrari.

Things worked beautifully to begin with. Massa scored a pole position at the 2014 Austrian Grand Prix, and managed five podiums over his first two seasons at Grove, helping propel Williams to two consecutive third places in the constructors' standings.

But this year has been much tougher. Williams has not been able to develop the FW38 effectively, and has been sucked back into a midfield battle with Force India and the resurgent McLaren team, rather than continuing its recent fights with Ferrari and Red Bull, or even kicking on towards challenging Mercedes at the front.

Massa is 35 years old, so very much nearer the end of his career than the beginning, and he is no longer racing for a top team, so no longer has any real chance of adding to the 11 wins and 16 pole positions he's amassed through his 15 seasons in F1.

Sustaining the absolute burning desire to improve and extract the best from yourself only gets more difficult with age, and even more so if your circumstances will not offer you a realistic chance to achieve your ultimate ambitions.

There is no doubt Massa is still a very capable grand prix driver. Let's not forget he raced for Ferrari for eight years, and came within a point of denying Lewis Hamilton the 2008 world championship.

Williams performance chief Rob Smedley told Autosport at the end of last season that Massa was still driving as well as he did during what would naturally be considered the peak of his career - arguably better given added experience, and that he'd been able to match highly-rated young team-mate Valtteri Bottas.

But therein lies the rub for Massa. He began this season by out-scoring Bottas over the first six races, but since then has slipped back - struggling to deliver consistent race performances. Bottas has also definitively out-performed Massa in qualifying, ahead 10-2 in the intra-team battle.

Williams has made no secret of the fact it is looking to shake up its driver line-up for 2017, with technical director Pat Symonds suggesting the team is now ready to attract a top driver, and holding talks with 2009 world champion Jenson Button about making a return to the team with which he began his career.

Having two drivers operating at a similar level is fine for a time, but if you want to kick on as a group you need drivers that can push each other to new heights in the car.

And if you have to choose between two drivers at a similar level, it makes sense to stick with the younger driver who has more potential and time to develop and improve, and a better likelihood of doing so - especially if that team has already taken the benefit of the older driver's greater experience.

Massa still has something to offer as a driver. Indeed sources in the paddock suggested he had sounded out other teams about possible opportunities to continue his career into a 16th season, though Massa himself says he has not held talks with other outfits - or discussions with Williams about continuing - despite previous utterances to the contrary.

But in reality options elsewhere were limited. A step up the grid was not on the cards, with Mercedes, Red Bull, Ferrari all full up for next season - and McLaren-Honda set to choose between Stoffel Vandoorne and Button for its one vacant seat.

Williams wants to make a change, Force India wants to retain Sergio Perez alongside Nico Hulkenberg; Toro Rosso is a team for Red Bull young drivers, Manor is becoming something similar for Mercedes pilots. Haas seems set on building its burgeoning operation around Romain Grosjean - experienced and five years Massa's junior.

Renault looked a potential destination had Massa wished to extend his 15-year stay at motorsport's pinnacle, especially given its public pronouncements about the desire to attract an experienced driver that can push the team forward.

But that is not the work of the moment, and Perez seems to be its top target. It's a five-year project at least, and Massa would likely not be able to remain there long enough for both parties to really feel the benefit of the rebuilding process.

It seems Massa has seen the way the F1 wind is blowing, and chosen his moment to go with the utmost dignity. He says he decided to stop "a few months ago", even though those closest to him were urging him to continue.

But his options to remain in a competitive seat were few and far between, and this way he can leave with his head held high, rather than clinging on grimly to the remnants of a career in decline.

There is a nice symmetry to choosing the Italian Grand Prix to make his announcement - 10 years on from Michael Schumacher's first retirement, which paved the way for Massa to remain at Ferrari, kick his own career onto a new level, and come so close to winning the world championship that has ultimately evaded his CV.

Perhaps his career would have followed a different trajectory had Hamilton not passed Timo Glock's gripless Toyota on the run to the finish line during that season's finale in Brazil?

But there's no point obsessing over the 'what ifs'. A driver of Massa's obvious calibre, with such an impressive track record, will be able to continue racing for many more years outside of F1 should he wish.

Top athletes often talk about wanting to choose their own moment to stop - to essentially jump before they are pushed. But few manage to pick the right time, or even realise the need to release what they hold so dear early enough to avoid seeing it ripped from their hands regardless.

All good things must come to and end eventually. Massa has recognised this, and chosen the right moment to call time on a fine grand prix career.