Former Australian Open finalist Thomas Enqvist believes if Roger Federer continues playing how he has in 2017 so far, he will become world number one by the end of the year.

The 35-year-old defied the odds as he returned from a knee injury after being six months out and went on to shock the world when he went all the way in Melbourne and won the 2017 Australian Open in January.

Federer then went on to win titles in Indian Wells and in Miami, climbing from 16th to fifth in the world rankings in the process while maintaining an impressive 19-1 record in the calendar year so far.

"It surprised me," Enqvist said, as quoted on Tennis World USA. "I am a big Federer fan. After injuries and a six month break, he played his best tennis not only at the Australian Open but also in all [the] other tournaments played, which is even more impressive."

Federer is currently taking a break ahead of the grass-court season and made headlines when he revealed that he would skip the French Open in order to concentrate on the upcoming grass and hard court events, mainly Wimbledon and the US Open.

Enqvist believes the Swiss ace made the right decision and that going by his current form, could find himself back on top of the world rankings by the end of 2017.

"If he continues like this, he can also be World No 1 at the end of the year," he added. "He took the right decision skipping the clay-court season to focus on grass and hard court events. He is one of the best athletes in the planet, he does everything being stylish."

Federer is expected to make his return after a 10-week break at the Mercedes Cup in Stuttgart with his first match set to be played on Wednesday (14 June).