Chelsea have been forced to watch European football from the comfort of their homes this season after failing to qualify last season.
Last night Arsenal booked their place in the quarter-finals of the competition with a victory on penalties against Porto.
Kai Havertz will be taking part in the latter stages in Europe again, with Chelsea fans in particular noting how his antics involving the Porto manager brought back some flashbacks.
The Champions League has been a proving ground for a number of talents this season, with scouts from clubs like Chelsea surely paying attention at all times.
One player may well have been on the losing side of the tie last night, however he proved across both legs that he can make the step up to a top side in Europe.
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Chelsea should sign Diogo Costa
Diogo Costa made a string of good saves last night to go with a clean sheet he picked up in the first leg of the tie.
The Portugal international has proven to be one of the most promising goalkeepers in Europe in recent years, and this has of course seen him linked to a number of sides in the recent past.
One of those has been Chelsea, who in the past have been linked with a move for around £65m.
The Blues have recently addressed the goalkeeper position by signing two players for the position in the same window.
While Robert Sanchez started the campaign between the sticks, he has since seen his place in the side taken by Djordje Petrovic, who has impressed greatly.
However, it has already been reported that not everyone is entirely convinced by the pair for the long-term future.
If this is the case, and they are to look to the transfer market again to sign a goalkeeper, they should look no further than Costa after seeing him prove his worth against Arsenal.