Top two's fight to the finish
1 Javier Hernandez has brought the best out of Wayne Rooney by allowing him to drop into the No 10 role, which showcases his imagination.
2 Rio Ferdinand's return gives Manchester United the best central defensive pair around. They've conceded just three goals in six games since his comeback from injury.
3 With two home games and a trip to Ewood Park, United's finishing straight should offer easier points and goals than Chelsea's fixtures.
1 Does Alex Ferguson know his best midfield? Ryan Giggs and Michael Carrick are in possession, but Anderson and Darren Fletcher merit places.
2 United will probably play Barcelona six days after the league concludes and the lure of the European Cup might distract them from the title.
3 United lost the title last year after a spring-time home defeat to Chelsea. "Squeaky bum time" might play with their focus on Sunday.
1 Chelsea have momentum in the Premier League. They have won eight of their last nine league games, and have taken 35 from the last 42 possible points.
2 With the January signings of defender David Luiz and striker Fernando Torres, as well as the return of midfield maestro Yossi Benayoun, Chelsea have the fresher legs.
3 With no European final, and the knowledge that Carlo Ancelotti's job is at stake, the Chelsea players have a clarity of purpose this month.
1 Three months after signing Torres, it is still not clear which strikers, and which system, best suit Chelsea. Dropping Torres is hard.
2 After Old Trafford, they still have to go to Goodison Park to face Everton. A tough place to gorge on goals.
3 Winning at Old Trafford this Sunday will be difficult. Visiting teams very rarely do so: and Chelsea must.