The one certain winner in the English Premier League title race will be the three-man defence.
Chelsea and Tottenham aren't just slugging it out for the title but also ownership over the tactical reconfiguration.
Mauricio Pochettino feels he isn't given credit for bringing the back three back into vogue last season, helping to propel Tottenham back into the English football elite by mounting consecutive credible title challenges for the first time.
Antonio Conte, who favoured the formation with Juventus, waited a couple of months into his reign to remove a man from his backline out of necessity rather than design.
With Chelsea trailing 3-0 at Arsenal and fading from the early season title running in September, the four-man defence was ditched at halftime. The leaks at the back were stemmed and Conte hasn't looked back. With eight matches remaining, there's a seven-point buffer between leaders Chelsea and Tottenham.
"People say now Chelsea changed the system," Pochettino said, "but no, we played always the three in possession", mainly to accommodate Eric Dier. Not to indulge the player but to bring out the best of the English graduate of the Sporting academy in Portugal and ensure he felt comfortable.
"He played like a midfielder without the ball, but with the ball, he was a third centre back," Pochettino said, assessing recent games. "You can see in possession, he dropped in between the centre backs or between the fullback and the center back, and always we play with three."
Pochettino is less rigid than Conte, returning to four at the back with a 4-2-3-1 depending on the opposition and player availability.
Tottenham's two favoured centre backs are Toby Alderweireld and Jan Vertonghen. A 3-4-3 or 3-4-2-1 formation allows the pacey Kyle Walker and Danny Rose to flourish, when fit, down the flanks as wing backs.
"We don't often have time to work on formations, only if we've got one game a week," Rose said. "Whatever formation we play, everyone knows their job."
Chelsea's use of wing backs has given Victor Moses a new lease of life. On the left flank, Marcos Alonso has shone through after establishing himself as a first-team regular. Gary Cahill, Cesar Azpilicueta and David Luiz are the favoured back three, although Moses' injury has forced Conte to rejig the line-up.
Chelsea and Tottenham have matches against teams lower down the standings tonight.
Tottenham host Watford after maintaining their pursuit of a first English title since 1961 by storming back to beat Swansea 3-1 with three late goals in six minutes on Thursday. Chelsea travel to Bournemouth fresh from defeating Manchester City 2-1.
With Liverpool five points further off the pace behind Tottenham in third, it seems certain the Premier League will have its first modern champion that largely relied on a three-man defence.
While Conte and Pochettino are both acclaimed for their tactical aptitude, they are hardly innovators.
Gareth Southgate sent England out with three at the back against Germany last month, 21 years after the coach featured in England's Euro 96 team with similar tactics.
At Barcelona, Luis Enrique recently switched from the more-established 4-3-3 to a 3-4-3 shortly after a demoralising 4-0 first-leg loss to Paris Saint-Germain in the Champions League in February. With an additional man in midfield, Barcelona were reinvigorated and a more attacking force, completing a remarkable comeback. AP