Wawrinka S. vs Murray A. prediction

We have big battle here at Roland Garros. World number 2 Andy Murray against world number 4 Stan Wawrinka. Head to head Murray leads 9-7 but these two have played only twice on this kind of surface and both matches Wawrinka won in straights sets 2-0. However these two matches were played in Roma 2008 and Monte Carlo 2013. Wawrinka had problems here against Rosol dropping two sets in opening round and he lost one set against Troicki. On the other hand Murray dropped two sets against Stepanek and Bourque and he lost one set against Gasquet. This should be really tough encounter and I expect both players to win at least one set. My pick is over 3.5 sets.