Boris Becker once shared a bitter rivalry with Ivan Lendl across the net and now the two former world number ones will try to outwit each other from courtside after the German's shock appointment as coach to Novak Djokovic.
After Djokovic was named ITF World Champion for 2013, despite being overshadowed by Spain's Rafa Nadal, Serbia's world number two announced the first shake-up of his team since a short and unsuccessful spell with Todd Martin in 2009.
Djokovic's decision to work with 46-year-old Becker means two of the current "Big Four" are now coached by former greats with Lendl helping Britain's Andy Murray to the 2012 US Open title and this year's Wimbledon crown.
"I am really excited to have the opportunity to work with Boris," the 26-year-old Djokovic said in a statement on his website.
"He is a true legend, someone who has great tennis knowledge and his experience will help me win new trophies from the grand slams and other tournaments. Becker is a great person, too, and I am sure he will fit in our team in the best possible way."
Becker, like Djokovic a six-times grand slam champion, will replace the Serb's long-time coach Marian Vajda, although the Slovakian will remain part of the team.
The last time Djokovic tinkered with his close-knit entourage he brought in former American player Martin but the relationship was terminated in 2010 after a less than fruitful year together.
Becker will travel to all the grand slam tournaments with Djokovic, starting with next month's Australian Open where the world number two is bidding for a fourth consecutive title, having twice beaten Murray in the final.
"I am proud Novak invited me to become his head coach," Becker, the youngest player to win Wimbledon when aged 17, said in the statement.
"I will do my best to help him reach his goals, and I am sure we can achieve great things together."
Becker and Lendl in opposite camps is an enticing prospect.
The 22 matches they played in the 1980s and early 90s always contained an undercurrent of friction, with the stony-faced Czech Lendl clearly agitated by the man nicknamed Boom Boom.
While Lendl edged their rivalry 12-10 it was Becker who won the three grand slam finals they contested, most notably the 1986 Wimbledon final which Lendl had set his heart on winning.
Becker once accused Lendl of not being "mentally tough" while Lendl hit back saying Becker did not have the guts to say things to his face in the locker room.
The passing of years has mellowed both men but their competitive edges will return in a few weeks when the new season starts with the build-up to the Australian Open.
Djokovic will hope Becker has a similar impact to Lendl's on Murray as he strives to regain the world number one ranking from Nadal who dominated 2013, winning the French Open and US Open titles on the way to the top of the rankings.
"My goal for 2014 is to play my best tennis and to get in shape for the Grand Slams and Masters 1000," Djokovic said.
"These tournaments have the most weight in our sport, and I want to prove my worth at them. The team is now strengthened and we hope for maximum results."
Djokovic will begin the year as ITF World Champion after surprisingly edging out Nadal for the award.
"Rafael Nadal made a remarkable comeback from injury with two grand slam wins, but it is Novak Djokovic's consistent results across all four Slams, Davis Cup and the ATP World Tour Finals that see him named World Champion," ITF President Francesco Ricci Bitti said on Wednesday.