Complex sentence: Manchester United will precede their 2014--15 campaign with a tour of the United States, during which they will participate in the 2014 International Champions Cup, playing against LA Galaxy, Roma, Internazionale and Real Madrid.
Split into simpler sentences: Manchester United will precede their 2014--15 campaign with a tour of the United States. They will also participate in the 2014 International Champions Cup, playing against Roma, Internazionale and Real Madrid.