'The job' Chelsea had to do was win, but their all-out defence only did part of that job - stopping us from scoring. The defensive tactics did not give them the win, it would not have happened without Gerrard slipping and Mourinho did not plan for that, nor was it brought about by his tactics.
So, they did well to stop us from scoring - but they only actually won the game through luck. Their tactics were good enough to get a 0-0, and if it had finished like that, Mourinho would be slagged off for being too negative.