MANCHESTER (Agencies) - Manchester United winger Nani has started the mind games ahead of Sundays (today) title-deciding visit of Chelsea by claiming his team-mates hold a psychological edge over their rivals. Sir Alex Fergusons side held a 15-point advantage over Chelsea two months ago and were seemingly coasting to a record 19th domestic title. But Chelsea have since eaten into Uniteds lead and arrive at Old Trafford just three points adrift with three games to play and with the Premier League title again in their sights following a run of five straight league wins. The momentum has shifted in recent weeks to set up a meeting that will leave the winners at the head of the table and favourites to finish top. But Nani disputes that Chelsea are in the ascendancy and says United are mentally in a better state of mind following their recent Champions League quarter-final win over their visitors. United proved too strong for the west Londoners last month, winning both at home and away, and the Portuguese winger says memory of their 3-1 aggregate success will help end Chelseas hopes of retaining the title for good. The results against them in the Champions League were very good, Nani said. We showed we can play against them and win both legs. I think that gives us the psychological advantage going into this critical game. We were not at our best in our defeat to Arsenal last week and we cannot be like that again in this one. We all realise we have to get back to our high tempo and confidence against Chelsea. We have to get back to our very best if we are going to do anything. It is always dangerous playing against Chelsea. They have some fantastic players. They are the team who every season are playing to win the league as well as us. They are always there challenging. We respect them but we have to be strong ourselves and just concentrate on what we do best and we can win it. It will be very difficult. But we are at home and we have had good experiences against them. If we win this one then it is a great advantage for us. It is nearly over then. United have collected a staggering 49 points out of a possible 51 on home soil this season and Ferguson knows another home win would all but wrap up the championship. The manager, who has confirmed striker Wayne Rooney is among those fit to return as he prepares to restore a host of regular first-timers, added: Everyone is aware of the magnitude of todays (Sunday) game. If we win, we should win the league. It is a game we are looking forward to. Last Sundays result (at Arsenal) has certainly brought us an awareness of how important this weeks game is. It is one of the reasons why I picked the team I did against Schalke (in the Champions League) on Wednesday. I wanted to give us a real chance. We will have a fresh team and that makes a difference at this time of the season. It should be a fantastic game. Carlo Ancelotti, the Chelsea manager, admits this is a do-or-die contest for his side, who looked to have no chance of retaining the title two months ago. Its like a final for us, he said. We wanted to play in the final of the Champions League but we have to be happy to play this kind of final. This is a different final but for us we can compare this game to a final. And he added: They (United) are favourites as they have three points more. If we are able to win, nothing is decided. If they win, they will win the title. Right-back Jose Bosingwa is the only Chelsea absentee and Ancelotti is anxious his side maintain the recent momentum that has turned their season around.