Juan Mata returns to Chelsea this weekend with his Manchester United place very much assured, and his team playing impressive football as they sweep aside all before them.
The Blues are top of the league by a decent margin, and eight points ahead of United, but Louis van Gaal's side will be looking to extend a five-match winning run by beating Jose Mourinho's men, who themselves haven't lost since New Year's Day.
And even more interestingly, Chelsea are yet to lose at home all season. It is no wonder that United's Spanish magician is likely to be key to any attempts to earn three points, and luckily the former Real Madrid youth is bang in form, with a goal or assist in his last three games.
Mata is likely to get a warm reception at Stamford Bridge, his first return there, after an impressive two-and-a-half year spell in West London.
Having joined the Blues in 2011 from Valencia, he promptly impressed Chelsea fans with both his goalscoring and creative play, and played a major part in successive European triumphs, first in the Champions League in his debut season and then the Europa League under Rafa Benitez.
Given that his attacking qualities outweigh his defensive work, it wasn't a great surprise to see Mourinho fail to utilise the Spaniard, though it still will rankle Chelsea fans that he was allowed to join Premier League rivals Manchester United.
After 33 goals in 135 games for the Blues, Mata had a slow start to life at Old Trafford, likely because of the team's general struggles last season, but the World Cup winner has come into Van Gaal's team with great success in recent weeks, and has 9 goals to his name this year.
Mata proved his worth in the difficult trip to Liverpool last month, scoring a brace to lead United to a 2-1 win, in what was the Reds' first league defeat of 2015.
With the 26-year-old returning to his old stomping ground, and facing players he knows only too well, you wouldn't put it past Mata being the difference again in what is a must win game for United, and a must not lose game for Chelsea.