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Friday 20 April 2012

Chelsea 5 Spurs 1.Who Made the Biggest Mistake?

Chelsea 5 Spurs 1,FA Cup Semi Final. 

How win probability can make sense of the game's two big talking points.

Scorelines can often hide a multitude of events that could have changed the course of a match and despite 2012's final score closely resembling the 5 goal thrashing handed out to Bolton by Stoke a year earlier,this game was far from one sided and potentially could have been even closer still.

Virtually all of the post game comment revolved around referee Martin Atkinson's inexplicable actions in awarding Chelsea a second goal despite being poorly positioned and receiving no conformation from his assistant.None of the players involved in the goal line scramble have subsequently confirmed that the ball crossed the line and Atkinson appears to accept that he erred in awarding the "ghost" goal.

Trailing 1-0 to Drogba's 45' strike,Spurs weren't in a particularly healthy position just prior to Atkinson's ill considered intervention.Their chances of turning the game around inside the 90 minutes of regulation time was no better than 8%,but they where right to be more optimistic about the likelihood of taking the match to 30 minutes of extra time.That possibility was just greater than a 20% chance and once into extra time they would hold a 23% chance of winning in the extra 30 minutes allowed.It was a coin toss as to whether extra time would peter out into a penalty shoot out,where there would be nothing to separate Spurs' chances of reaching the final from that of Chelsea.If we combine all the possible routes that were available to Spurs in their quest to return to Wembley in a fortnight's time,they total 18% or roughly a 9/2 chance.

 Once Atkinson had blown his whistle to award Mata his goal the 90 minutes odds for Spurs all crashed.They  were about 60/1 to overturn their now two goal deficit inside the 90 minutes and they were about 15/1 to take the game to extra time.Overall the "goal" combined with the three minutes that had elapsed since Chelsea's opener had dropped their 18% chance of appearing in the FA Cup final down to only 5%.Their potential chances in extra time hadn't changed,but their chances of getting that far or completing a turn around in the 90 minutes certainly had.

Spurs' chances when trailing 1-0 just prior to the 48' "ghost" Goal by Mata.

Game
Period.
Spurs' Win
Probability.
Spurs' Draw
Probability
Spurs' W/DP in 90 minutes. 8.0 20.9
Spurs' W/DP in Extra Time. 23.1 51.3
Spurs' WP in Penalties. 50.0 NA

Spurs' combined chances of Qualifying for the FA Cup Final,18%

Spurs' chances when trailing 2-0 immediately after the "Ghost" Goal.

Game Period. Spurs' Win
Probability.
Spurs' Draw
Probability
Spurs' W/DP in 90 minutes. 1.6 6.4
Spurs' W/DP in Extra Time. 23.1 51.3
Spurs' WP in Penalties. 50.0 NA

Spurs' combined chances of Qualifying for the FA Cup Final,5%

If the Atkinson incident was infuriating for the Spurs fans,players and management,they were about to be subjected to the most bitter sweet moment in the history of the FA Cup.Spurred onto the offensive as trailing teams often are,Adebayor broke clear of the Chelsea defence,knocked the ball wide of the onrushing Cech and was felled inside the box by the Chelsea keeper.A penalty and a red card for Cech was a formality until Gareth Bale who had been supporting Adebayor's break ran onto the loose ball and calmly stroked the ball into the net.Atkinson awarded the goal and correctly allowed Cech to stay on the pitch,although he probably should have yellow carded the keeper for his challenge on Adebayor.

2-1 to Chelsea,11 verses 11 and 40 minutes of normal time to go.

It was a perfectly natural reaction from Bale.....but was it the correct one to give his side the best possible chance of getting to the final.Immediately you sensed he would have been better ignoring the ball and allowing Atkinson to award the penalty and dismiss Cech.

An almost unique situation and Bale had only a split second to decide what to do,but everything pointed to a red card and a penalty favouring Spurs more than just the goal.Firstly,penalties are converted at rates in excess of 70%,so they were odds on to score.Next the game still had almost 40 minutes to run making a red card alone worth almost 7 tenths of a goal to Spurs.And lastly,the possibility of extra time increased the potential benefit that Spurs would gain from a Cech dismissal.

If we do the win probability maths we find that the two different scenarios aren't even close and I've listed the individual win probabilities for all scenarios in the tables below.By scoring the goal,Bale lifted his team's chances of qualification to 17% just shy of the levels they were at prior to Chelsea's second goal.But if he'd resisted the open goal and Spurs were lining up a penalty kick against 10 man Chelsea's second choice keeper,their chances of reaching Wembley again in May would have stood at a substantially greater 34%.Never should a goal by your team have been celebrated with such less enthusiasm as this one.

Incredibly by scoring Bale had halved his team's chances of getting to a cup final.Had he resisted the chance we could have seen a clued up Chelsea defender desperately trying to slam the ball into his own net before Atkinson could blow his whistle to award the spot kick.


Bale Scores in the 56' to make the score Chelsea 2 Spurs 1.

Game Period. Spurs' Win
Probability.
Spurs' Draw
Probability
Spurs' W/DP in 90 minutes. 6.8 20.6
Spurs' W/DP in Extra Time. 23.1 51.3
Spurs' WP in Penalties. 50 NA

Spurs' combined chances of Qualifying for the FA Cup Final,17%

Bale Shuns the chance,Cech is Red Carded and Spurs are awarded a Penalty.Chelsea 2 Spurs 0.


Game Period. Spurs' Win
Probability.
Spurs' Draw
Probability
Spurs' W/DP in 90 minutes. 15.8 27.2
Spurs' W/DP in Extra Time. 41.2 49.0
Spurs' WP in Penalties. 50 NA

Spurs' combined chances of Qualifying for FA Cup Final,34%.

Both incidents were honest mistakes and Atkinson would certainly reverse his if given the chance,but how many could say,hand on heart what course they would have taken faced with Bale's dilemma,even in full possession of the Win Probabilities for each outcome.

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