With Chelsea chasing the title and West Ham scrapping for survival back in January this year, Sam Allardyce took his Hammers across London to Stamford Bridge and essentially gave Jose Mourinho a taste of his own medicine.
West Ham left with a 0-0 draw, and the stats were frankly incredible. West Ham had just 28% of possession, had one shot on goal, whilst Chelsea peppered the Hammers goal with a whopping 39 shots - but couldn't find the elusive winner.
Mourinho was fuming after the game, suggesting that Allardyce's men played '19th century tactics' and parked the bus, something Mourinho's Chelsea have become famous for in the past.
Fast forward to this season, and West Ham sit in fourth place, 11 points behind league leaders Chelsea after a superb first half of the season from Allardyce's side.
There's renewed vigour in the way West Ham play, with creativity and pace in the final third, but still with the threat of the direct crosses which serve Andy Carroll so well.
Ahead of the meeting between the two sides on Boxing Day, Mourinho says that he's impressed with how West Ham have played this season, and doesn't expect them to park the bus again.
"To be fourth for a team that everybody was expecting to fight for survival, I think that is a fantastic achievement...very good," said Mourinho.
"I think both teams are different than last season. We are a better team; we have more creativity, we have more goals, we have more attacking dynamics...and West Ham is also a better team. "I think they are not a team in this moment just to try not to concede. I think they also try to score goals, so the game will be very difficult. I think both teams have the capacity now to give a completely different game," he added.
Mourinho's acknowledgement of West Ham's quality is just yet another sign of the progress being made at Upton Park this season, and having already beaten Liverpool and Manchester City this season, they travel to Stamford Bridge in the hope of getting a positive result.
Yet with Allardyce, you really can't rule out the possibility of him 'parking the bus' again and frustrating Mourinho for the second time in less than a year. The fact is that with this squad at his disposal, Allardyce can change things up and play in a number of different ways - and that's a large reason for their success so far this term.