Roger Federer's possible retirement from tennis has been a dark topic over the last few years. Widely regarded as the greatest tennis player in the entire history of the gamey, the 36-year-old conquered any doubt by delivering a great deal of tennis since his comeback from injury.

Approximately 14 months after conquering Melbourne for the first time since 2010, Roger Federer saw his spell fading away as he failed to defend the Sunshine Double success of 2017. He was pretty close to securing his spot at Indian Wells but a clear-headed Juan Martin del Potro and several crucial mistakes cost him the title.

Another worrying sign emerged in miami as Federer lost his second round rubber against Thanasi Kokkinakis despite being a set up against the Aussie player.

Roger Federer's schedule will leave no room for clay

Immediately after losing to Kokkinakis, Federer went public on his decision to skip the entire upcoming clay court season, including the 2018 French Open. Therefore he ended some rumors about him being a factor in the upcoming outdoor clay swing in Europe.

The Swiss player is set to pursue another grass court winning streak. But that also means he will step off the radar for the next couple of months since the grass season is set to begin in mid-June. If we get lucky, Federer will follow the same script as in 2017 which means he will make an appearance at the Mercedes Cup in Stuttgart first.

Then, the Gerry Weber Open in Halle would be his second spot on the list. Finally, he would seek another Grand Slam success at the 2018 Wimbledon Championships.

When it comes to the summer swing on hard courts, Federer made a mistake last year by choosing to play the Rogers Cup in Canada. It all ended up with an injury that hampered his plans for the US Open.

This time he might go to Cincinnati instead, a tournament that is known for having some of the fastest courts on the tour.

2018 US Open stands as the main target for the second part of the season. It's been almost 10 years since Federer won the title at Flushing Meadows and, with a bit of luck on his side, he might change that too.

Roger Federer showing his age might bring a bitter feeling

Roger Federer lost in Miami to a well-prepared opponent as Kokkinakis seemed prepared to offer no free homage whatsoever. Moreover, Federer lost back-to-back matches for the first time since 2014.

Although showing your age is not a harm-causing thing in general, in his case though, it meant a lot. Letting his opponent seeing his vulnerability was a trigger, as Kokkinakis became aware of his chances.

There were a lot of similarities between this particular match and the one between Federer and Borna Coric. At Indian Wells, the young Croatian caved in just when the finish line was in his sight. But Kokkinakis made it through in one piece by not letting the emotions suffocate his mind and his game.

On the other side, Roger Federer has offered a sample of his mortality, something we had been choosing to ignore over the last year or so.