The Irishman arrived a year ago from AC Milan.
He told the club's website: "Pre-season is key to getting as fit as possible going into the season, trying to get some minutes under my belt and getting as close to match fitness as I can. I wouldn't say it's my favourite time but you've got to do it. During the season, you then reap the rewards and that's why you put all the work in early.
"It was important for us to end the season on a high and, hopefully, we can now bring that energy into this season. Everybody is looking forward to it, whether we win the same trophy again or we look for more. We are all excited to getting the season started and seeing how we get on.
"Coming to a new club is always difficult but I think I settled in easily, playing so many games that I think I've learned so much from all of that and I'm ready to bring all of my experiences from last season into this one."