Sentence:  In the build-up to the second spot-kick, Villa-Boas felt United striker Danny Welbeck had deliberately tripped over the leg of Branislav Ivanovic rather than an intentional foul being committed. "Referees have pretty clear orders on <WSD>simulation</WSD>, but it is difficult for them to assess the difference between <WSD>simulation</WSD> and fouls in those situations," he said. 
Meaning of the word marked with <WSD> tags:  The act of falling over in order to be awarded a foul, when no foul has been committed.