Is Carlos Alcaraz the greatest 21-year-old ever? The debate rages on

At 21, Carlos Alcaraz has won four major titles, a career milestone that eluded even greats such as Roger Federer, Rafael Nadal, Novak Djokovic and Pete Sampras.

The Spaniard's rapid rise to the top of the food chain has led some to pronounce him the greatest 21-year-old in men's tennis history.

Fachan makes a compelling case.

To add to the mentioned list above, Alcaraz is the youngest player to complete the Channel Slam (Roland Garros and Wimbledon in the same year) and the Surface Slam (major wins on grass, clay and hard courts) besides being the youngest World No. 1 ever at 19 years and 129 days.

Alcaraz is also the first outside the "Big Three" to win four majors in the 21st century, a feat that eluded Andy Murray and Stan Wawrinka, the only others to win at least three majors since the year 2001.

All that said, Alcaraz is not the youngest to win four majors at 21 years and 70 days — his age when he beat Djokovic for his second Wimbledon title on Sunday. Two others before him achieved the feat a little earlier than he did, and another iconic player came very close.

Bjorn Borg

After winning the 1974 French Open as an 18-year-old, Borg would successfully defend his title the following year. By the age of 21 years and 28 days, the Swede had captured the Roland Garros and Wimbledon on two occasions each. That's nearly 50 days quicker than Alcaraz.

How does Alcaraz stack up here?

It's probably Advantage Alcaraz since Borg never won a hard court major, losing four US Open finals in his career and failing to advance past the third round at the Australian Open.

The US Open often switched surfaces during the 1970s, but Borg's wins were still restricted to clay and grass. Furthermore, he did not become World No. 1 until August 1977 when he was a 21-year-old, two years after Alcaraz.

Mats Wilander

Following in the footsteps of Borg, this Swede also got off to a rollicking start as a teenager. After capturing the 1982 French Open as a 17-year-old, he followed it up with back-to-back Australian Open titles in 1983 and 1984. A few months before his 21st birthday, Wilander would capture his fourth major title, the 1985 French Open.

As such, Wilander captured his fourth major title a little earlier than Borg and Alcaraz, at the age of 20 years and 10 months.

Wilander has a strong argument for the "greatest 21-year-old ever" title, but his inability to succeed on the grass courts probably weakens his case. The Swede never got past the quarters in Wimbledon.

Honorable Mention: Boris Becker

Becker captured his first two Wimbledon titles (1985 and 1986) as a teenager but had to wait another three years before his next two majors — the 1989 Wimbledon and 1989 US Open. As such, the German icon was roughly 21.5 years old when he reached the four major thresholds.

Alcaraz's legacy will eventually be determined by his longevity, for many of the greats saw a dip in performance as they entered their mid-20s and 30s. But it's hard to argue that the Spaniard is as elite of a 21-year-old that the sport has ever seen (including the women's game).