The German, a former world number one, believes no amount of praise is enough for the duo's achievements, despite them suffering numerous setbacks in terms of injuries and loss of form.
Federer and Nadal dominated the men's game for almost a decade since they first played each other at the Miami Open in 2004. They have a combined 36 Grand Slam titles between them and are arguably two of the greatest to ever play the game.
However, their ability to challenge for major titles on a regular basis was questioned when they both struggled with injury in 2016. There were doubts if they could return to the top or even play regularly on the tour.
Federer and Nadal silenced their critics in fine fashion when they returned from their respective six- and three-month injury lay-offs at the start of the 2017 season. The former started the year as the world number 18 and the latter was ranked number eight, but they ended the season as the number two and one player, respectively. Federer has since taken over at the top, with Nadal currently in second place.
In the last 13 months, Federer and Nadal have won a combined 15 titles, which include all five Grand Slams. The Swiss ace won the 2017 and 2018 Australian Open titles and the Wimbledon Championship last year, while the Spaniard picked up his tenth French Open crown in 2017 and his third US Open in September last year.
Becker was among the doubters earlier, but is full of praise for them following their comebacks. He believes that it was possible only due to their love for the game as they had nothing to prove to anyone owing to their dominance in the past.
"I can't praise Roger and Rafa enough. When I heard that both players were taking four, five, six months off, I was very doubtful that Roger would come back, especially given his age and in Rafa's case, given the nature of his style – he's a very physical player," Becker said, as quoted by the Express.
"But they've proven everybody wrong. How much determination, willpower, discipline but, ultimately, the love for the game they must have because they're champions.
"They don't need to come back. They made enough money, enough No. 1 rankings and all that. So the only reason for them to come back is because they love to compete and they love the game," the German six-time men's singles Grand Slam winner explained.
"We can't praise them enough or give them enough awards for this. Once they stop, we will truly understand their accomplishments."