There isn't a much better way to come storming back into your former home than the way Paris Saint-Germain's David Luiz did at Stamford Bridge on a damp London night.
The Brazilian moved from Chelsea to PSG this summer in a £50 million swap, and although his price tag raised some eyebrows, his goal against his former club could be worth every last pound. Without his goal, PSG would not have beaten Chelsea 3-3 on aggregate, edging the home side thanks to away goals.
Reduced to 10 men after a ridiculous red card to striker/Swedish god/egomaniac/autobiographist Zlatan Ibrahimovic after 31 minutes (we'll come back to this later), PSG was looking at its second straight year of being dumped from the Champions League by the London club. An 81st-minute goal from defender Gary Cahill put the aggregate score at 2-1 to the home side.
Five minutes later, Luiz stuck a dagger into the side of his former club.
A mere four minutes before a second heartbreaking exit, Luiz hit a bullet header onto the underside of Thibaut Courtois's crossbar, the spindly Belgian watching on helpless as the away side drew level.
Without this goal, PSG would not have sent the game to extra time, eventually drawing 2-2 with Chelsea.
There's an unwritten rule that, when former players return to their old clubs, they should not celebrate a goal. It's in good taste. Remember the good times and that.
David Luiz cares not for unwritten rules. After the goal, he wheeled behind the goal, mean mugged the crowd (albeit into the away team's section) and went to his knees to celebrate.
The goal was priceless for him, too.
GOOD DIEGO/BAD DIEGO
Diego Costa is a bad man who happens to be one hell of a player.
Like many before him, he has a mean side to his game. When he's not scoring goals, he's irritating the living hell out of his opponents by hook or crook.
He could have had a greater impact on last night's game had the referee been willing. Costa was denied what seemed to be a certain penalty minutes after Ibrahimovic was sent off — with the referee perhaps scared to insert himself into the game further after the red card.
But it was Costa who was on the wrong end of the battering. He was elbowed by Luiz and Javier Pastore, and had his ankle hacked at by Edinson Cavani. He was often left writhing on the ground, beaten at his own game by PSG.
The tactic worked for the French side, keeping Costa off the score sheet (his touch before Cahill's goal, a skewed shot, should be an assist in hockey only).
Costa, scorer of 17 goals in 21 games in the English Premier League, finished his 2014/15 Champions League campaign with no goals to his name.
CHILL, CHELSEA
Back to the Ibrahimovic sending off.
There is another unwritten rule in soccer — don't try to influence the referee to get someone sent off. Like celebrating against your old team, it's just in poor taste.
When Ibrahimovic went in clumsily against Chelsea's Oscar, nine Chelsea players decided to ignore that rule.
Whether or not the reaction from the Chelsea players worked is up for discussion. It seems like the referee went straight for the red card pretty quickly, possibly making up his mind before he heard any protest from the players.
And like most unwritten rules, this one is bullshit. In the eyes of the Chelsea players, Ibrahimovic went in pretty heavily on Oscar and they're standing up for one of their own.
But, like I've said before, nobody clutches their pearls like the English media. At halftime, former Liverpool player and Sky Sports pundit Jamie Carragher called the reaction "disgraceful" and "sad."
Like Luiz celebrating against his old club (for which he later apologized), media types will use these incidents to feed into fans' dislike for one team or another with chatter about these unwritten rules. Luiz's celebration and the Chelsea reaction might have left a bitter taste in the mouth of a few, but what's at their core? You have a player celebrating a fine goal and a team standing up for one of its own.
There's nothing wrong with either action, and to focus on either takes away from what was a thrilling game.
To hell with unwritten rules.