Rafael Nadal returns to competition in Abu Dhabi on Friday with his expectations low after a lengthy injury absence but hopes high of lining up in next month’s Australian Open. The 20-time major champion has struggled with a foot injury for the past six months -– forcing him to miss both Wimbledon and the US Open. His first event in four months is the Mubadala World Tennis Championship exhibition where the Spaniard will face another former world number one Andy Murray or Dan Evans on Friday. Nadal is guaranteed to get two matches under his belt in the UAE capital, which will help him assess th…