Former British tennis player Barry Cowan believes Roger Federer is not a certainty for Miami and that the Swiss ace will make a decision on whether to play following his participation at Indian Wells.

The 36-year-old became the first male tennis player to win 20 Grand Slam titles following his triumph at Melbourne, where he successfully defended his Australian Open title, beating Marin Cilic in the final.

Federer followed that up by winning the Rotterdam Open, picking up his 97th career title in the process. On his way to the final, he also became the oldest player to top the ATP rankings. He broke Andre Agassi's long standing record – the American was 33 when he reached the summit in 2003.

Since then, he has decided to pull out of the Dubai Open Championships, citing a need to spend more time with his family, before preparing for the American hard court scene with Indian Wells and Miami.

Federer is the defending champion at both these events, having won the Sunshine Double for the third time in his career last year, and will be looking to strengthen his grip at the top of the rankings with another memorable performance.

However, Cowan believes that Federer's participation in Miami is still up in the air and that a decision is likely to be made after Indian Wells, depending on his fitness.

"What Federer has shown is that he knows when to pick and choose what tournaments he enters because he doesn't want to overplay," Cowan told Sky Sports. "He will identify what are the most important tournaments and then ask himself, 'What do I need to do before that to be ready?'

"Indian Wells will be his number one priority more so than Miami, so he will try to do the best he can to play in the desert.

"He will play Indian Wells and then he will see how he feels after that and whether he commits to playing in Miami. I don't think Miami is a certainty."

Roger Federer
Roger Federer is the oldest world number one Getty