Scoring a seemingly vital away goal is often the main objective of clubs going into UEFA Champions League first legs, but that away goal may not be quite as important as it’s made out to be.
When a club returns home with a 1-1 road draw it is usually hailed as a success. They’ve scored their away goal, they don’t have any catching up to do and as the whistle blows to start the second leg they are in an advancing position.
A 0-0 draw however is met with scepticism and uncertainty. Neither team has the upper hand when the second leg begins and while one team enjoys home field advantage they know that if they go behind they will have to score twice to recover.
Conventional wisdom says that a 1-1 first leg draw puts the home team in the driver’s seat for the second leg, while a scoreless draw in the first leg leaves everything to play for.
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On the surface this makes sense. However, looking at Champions League results since the introduction of two-legged knockout ties in 1994 there simply isn’t that big of a difference between 0-0 and 1-1 draws.
During this period, 31 first-leg ties ended 1-1. In the following second legs, the home team won 20 times and the away team won 10 (with one 1-1 draw that sent the tie to penalty shots). This means that after drawing the first leg 1-1 away from home, teams went through 65 percent of the time.
This seems to fall in line with what we would expect. We treat a 1-1 draw away from home as a good result and the data agrees. These teams tend to go through about two-thirds of the time. What is surprising is what happens when we look at the results after scoreless draws in the first leg.
Twenty-six Champions League first leg ties have ended 0-0. Traditionally we’ve been told this puts the tie perfectly in the balance, but this doesn’t seem to match what we see in practise. In the second leg following a scoreless draw, 66 percent of the home teams won the game and by extension the tie. This is almost identical to the 65 percent of home teams that advanced in the second leg after drawing 1-1 away from home.
The away team won the second leg 19 percent of the time after scoreless first legs, and the game ended in a score draw—a draw in which both teams score at least one goal—15 percent of the time (although the result is essentially the same since a score draw sends the away team through after a 0-0 first leg draw).
It makes sense that there would be more score draws in second legs following scoreless first legs since away teams try and hold onto these score draws that send them through to the next round.
What do these two sets of results tell us? Essentially that in the Champions League a 0-0 draw and a 1-1 draw both give a similar advantage to the home team in the second leg. This starts to bring into question the approach of some away teams in the first leg of Champions League games that open up at the back in order to chase an away goal.
The one caveat on these findings is that although the hosts of the first and second leg are drawn randomly in the quarterfinals and semifinals, they are not in the round of 16. In the round of 16 the teams finishing first in their group always host the second leg, and thus usually start the tie as favourites. This seeding slightly skews the probability of the home team advancing after a first leg draw.
Looking ahead to this week’s second leg ties in light of these results we have a better idea of each team’s chances of progressing.
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Chelsea came away from Paris with a 1-1 draw and Porto returns to Portugal having earned a 1-1 draw in Basel. Both Chelsea and Porto will be pleased with these results and their chances of moving onto the quarterfinals.
One of the standout results of the first round games was Shakhtar Donetsk’s scoreless draw with German powerhouse Bayern Munich. Playing in a neutral venue, outside of their league season many lauded the performance of Donetsk saying it gave them a fighting shot to progress in Munich. Obviously, Donetsk still have a chance but given that the home team has progressed 66 percent of the time following scoreless first legs Bayern Munich have to be made heavy favourites to go through.
Inevitably this week many commentators and pundits will hold up Chelsea and Porto’s first leg results as positives while saying that the Shaktar-Bayern tie is still in the balance, but in reality Chelsea, Porto and Bayern are all going into their second leg ties in very similar positions.
Sam Gregory is soccer analytics writer based in Montreal. Follow him on Twitter