Match statistics: Chelsea 2-0 Tottenham
When Chelsea agreed to pay £38 million ($49m) to sign Hakim Ziyech from Ajax in the winter of 2020, they thought they knew what they were getting.
A wizard with the ball and with a wand of a left foot, the Morocco international was signed to add an X-factor to an attacking unit that was young and energetic but lacked a bit of guile.
Ziyech's first 18 months at Stamford Bridge, then, have been something of a disappointment.
He came into Sunday's clash against Tottenham with just four league goals and five league assists to his name in a Chelsea shirt, and with question marks over his attitude after his moody reaction to scoring from long range against Brighton in midweek.
Next Match
But on a day when Thomas Tuchel was crying out for an X-factor in front of goal after a frustrating first half, Ziyech produced a moment of quality that harked back to his Ajax days, and could be the catalyst for him to finally start producing on a weekly basis for the Blues.
Spurs came into the game having not lost a league match since Antonio Conte took charge in November, while Chelsea had not won in four and had taken just eight points from the previous 21 available during a spell that has seen them fall out of the title race and tumble towards those challenging for fourth spot.
After a goalless first half that Chelsea largely dominated but could have fallen behind in had Harry Kane not been penalised for a push on Thiago Silva before firing into the bottom corner, Ziyech wasted little time in working his magic as he cut inside around 20 yards from goal before bending a supreme effort past a frozen Hugo Lloris and into the top corner.
"How good was the goal? I think it was 10 out of 10!" Ziyech told Sky Sports post-match. "I thought maybe I hit it a lttle bit hard, but in the end I saw it go in."
Remarkably, it was Ziyech's first league goal at Stamford Bridge, and what a way to do it. Ajax fans grew used to him producing such moments, and Chelsea fans will hope to too after his slow start to life at the club.
It seems, though, that Ajax may have provided Ziyech with the inspiration he needed to score such a goal with their own efforts on Sunday.
A couple of hours before kick-off in London, Ajax were celebrating their own victory, as Noussair Mazraoui's own curling effort bounced in off the post to secure a 2-1 win over PSV in what many believe could prove to be a title decider in the Eredivisie.
Mazraoui revealed post-match that Ziyech had been watching, and had sent a message on Whatsapp to his former team-mate, joking that the full-back's winner was "a horrible goal".
Whether seeing his former side produce such a moment reminded Ziyech of his own ability or not, his overall performance was that of a player who is rediscovering his confidence.
Tuchel set up his side in a 4-3-3 formation that had Ziyech, Mount and Callum Hudson-Odoi switching positions throughout the 90 minutes, with the trio laying on a number of chances that on another day would have been finished by Romelu Lukaku.
Hudson-Odoi claimed the assist - or at least the final pass - for Ziyech's goal, before winning the free-kick that Mount delivered onto the head of Thiago Silva for Chelsea's second of the afternoon.
GettyZiyech eventually left the field to a standing ovation as he was substituted in the final minutes having suffered from a bought of cramp that was no doubt brought on by a display that was not just thrilling in attack, but also saw him work hard to press and win the ball back to help Chelsea keep their first Premier League clean sheet in seven matches.
"It was one of his best matches today because he was very reliable," Tuchel said of a player who, had he not fallen out with Morocco manager Vahid Halilhodzic, would have been at the Africa Cup of Nations right now. "It was also maybe he best position to be on the wing. We had the wide position on the right wing, that position does not normally exist in that particular manner when we play 3-4-3, it is more of a wing back. Maybe we can think about doing this (more).
"It was good because it gave him the opportunity to take risks where it was possible to take risks. He was very reliable on the ball in moments where it is necessary.
"The work rate was always outstanding. You can always rely on him for work rate and counter-pressing. So yes, well done and he needs to keep on going like everyone else."
GettyThe importance of this win cannot be understated. Tuchel had described his team as being "mentally and physically tired" after the Brighton draw, with the Blues having played more games (18) since the November international break than any other Premier League side - a point the club have been keen to hammer home in recent days.
Now the players will who are not away on international duty in the coming days will be given a week off to recharge their batteries before their FA Cup fourth-round tie against League One outfit Plymouth Argyle on February 5.
From there, they will head to the United Arab Emirates for the Club World Cup, with their meeting with Crystal Palace on February 19 the only league match they will play between now and the first weekend of March.
By the time that Palace game comes around, some of those teams in the battle for fourth may have closed the gap on Chelsea, but beating Spurs ensured that they will return to the competition still sat third in the table.
Ziyech's wizardry was the catalyst for that, and the hope now is that he can continue to cast his spells through the second half of the campaign so that Chelsea's miserable winter can be put behind them.