Pat Nevin analysis: Why Jose Mourinho is 'the Radical One'
BBC Sport's Pat Nevin looks at how the tactical switches and formations employed by Chelsea boss Jose Mourinho during matches can influence results.
Chelsea travel to Arsenal on Monday knowing victory would put Mourinho's men level on points with Premier League leaders Liverpool.
Nevin believes that no other manager responds as quickly, or uses as many unconventional formations as Mourinho while a game is in progress.
The Portuguese is in the first season of his second spell at Stamford Bridge, where he twice won the Premier League title between 2004 and 2007.