Frank Lampard's done the double. Saturday's 2-1 win over Tottenham means his Chelsea boys are the first team ever to beat a side managed by Jose Mourinho home and away in the same league season.
Throw in last season's Carabao Cup win, when Lampard's Derby knocked Mourinho's Manchester United out of the competition at Old Trafford, and the managers' head-to-head record is three from three for the apprentice against the master.
Lampard was humble and keen to downplay the tactical battle between himself and his former Chelsea boss in his post-match press conference but this was a significant victory. While Chelsea's set-up may not have caught Tottenham by surprise as it did in December, their fast, aggressive approach was too much for their conservative, injury-hit opponents.
This win was a timely one too, after a worrying run of results.
Four Premier League games without a win, and a longer streak of just four victories in 14, had seen Lampard's young Chelsea side - hit by inconsistency and injuries themselves - squander what had been a commanding advantage in the race for a top-four finish.
As Mourinho was quick to point out in the build-up, Spurs had been 12 points adrift of their London rivals when he took over from Mauricio Pochettino in November. A win at Stamford Bridge would have lifted Spurs above Chelsea in the table. The pressure was on for Lampard.
It had been a rough start to the week, too, with an out of sorts Manchester United adding to Chelsea's miserable home record on Monday night, amid a series of frustrating VAR calls for the hosts at Stamford Bridge. That result compacted the group of top-four chasers even further.
Suddenly, the leeway Lampard had been afforded in pre-season, with the mitigation of a transfer ban, Eden Hazard's sale and a remit to build with youth, felt a long time ago.
With the team falling below the standards they had set in the first half of the season, Lampard was this week left to field questions about the financial impact of failing to qualify for the Champions League. Never mind the fact Chelsea's fourth place position in late February would have been viewed as an impressive achievement back in the summer, when all the talk was of 'transition'.
Lampard's reaction was to change formation. It was a move which could easily have been undermined when Mourinho revealed on Friday he had been told about Lampard's plans to switch to a three-man defence - "you don't tell the sources". But it had worked for Chelsea previously this season - most notably at the Tottenham Hotspur Stadium - and forced Mourinho to alter his own set-up.
Lampard's other reaction was to change personnel. There were four changes from the defeat to Manchester United, with Olivier Giroud, Marcos Alonso, Mason Mount and Ross Barkley all coming in.
The result was emphatic - even if, as Lampard said afterwards, a VAR error, a late own goal and some missed chances from Chelsea affected the look of the scoreline. Mourinho may have known what was coming but he couldn't find a way to stop it.
Barkley, making his first Premier League start since early January, added energy, pressing and pace with Mount around Giroud. While Mount made twice as many sprints as any of his team-mates (20), the French striker - on his first start since November 30 - gave Chelsea a figurehead to aim for and to play off against Spurs' deep defence.
Alonso, recalled for the first time in the Premier League since the reverse fixture in December, added attacking impetus on the flanks, covering a game-high 11.28km.
It's credit to these players - particularly goalscorers Giroud and Alonso - that they had such an impact after coming in from the cold. But Lampard's use of his squad and ability to adapt the way his side set up should earn the young manager plaudits, too.
All four of those players combined for Chelsea's excellent second goal to underline the point.
A downbeat Mourinho listed Chelsea's variety of attacking options in contrast to his own - "zero" - after the game but overlooked the facts - Lampard has a 38-year-old in goal, three wingers in the treatment room and his best midfielder, N'Golo Kante, out injured too.
Those issues and absences could well lead to Chelsea being outdone by Bayern Munich in the Champions League on Tuesday night. But domestically Chelsea are now back in a commanding position as they seek to qualify for that competition again next season.
And in a week when Lampard has faced up to managerial mind games, handled the pressure put upon him and come up with solutions to steer his side back on course, victory over Spurs could be an important moment in the apprentice's development.