The Champions League knockout stages are regularly some of the football season's most exciting matches, with Europe's elite clubs all vying for a shot at the greatest prize in club football.
The two legged ties have often brought edge of the seat action and this year will be no different, with Chelsea and Tottenham both hoping that they can overturn first leg deficits to progress to the quarter finals.
On Tuesday night, Graham Potter's Chelsea side welcome Borussia Dortmund to Stamford Bridge, with a one goal first leg deficit to overturn. Their confidence will have been boosted by the weekend's narrow 1-0 win against Leeds in the Premier League, but the Bundesliga side will present an altogether different test.
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Tottenham, meanwhile, welcome AC Milan to North London with their confidence having slipped in recent weeks amid the absence of Antonio Conte from the touchline. Four defeats in their last six matches, with a 1-0 defeat at the San Siro means that Rossoneri travel to the Tottenham Hotspur Stadium as favourites to progress.
Here are the Champions League knockout round rules you need to know:
What happens if the scores are tied?
With the margins so fine, both Chelsea and Spurs will know that a strong showing and a narrow win could level the tie and send it into extra time and penalties if needed. In previous years, the only way that such an outcome occur would be matching the first leg score, with a 1-0 win and subsequent 1-1 aggregate scoreline being the only way that extra time could be forced.
Does the away goals rule still apply?
However, since the away goals rule was abolished at the beginning of the 2021/22 season, it now means that so long as the scores are level at the end of 90 minutes, then extra time will be necessary to separate the sides. This means that even if either record a 2-1 win then extra time would still be necessary with a penalty shootout at the end of the additional period as long as scores are still level.
Away goals had previously precipitated high levels of drama in the knockout stages, with ties often placed on a knife-edge by the jeopardy of the rule. Away goals were abolished after the 2020/21 season, when the COVID-19 pandemic forced ties to be staged at neutral venues, rendering the rule needless
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