London:Cristiano Ronaldo scored two second-half goals to help Manchester United beat Wigan 3-1 on Tuesday and extend its lead atop the Premier League to four points over Chelsea, which drew 2-2 with Reading. Man United has 50 points after 20 games and Chelsea 46. Second-half substitute Ronaldo headed in a cross from Paul Scholes in the 46th minute to score first. Wigan goalkeeper Kris Kirkland saved Ronaldo's penalty in the 50th, but the Portugal winger shot the rebound in for his 10th league goal of the season to make it 2-0. "I had a feeling he would change the game. Cristiano is in such great form, it was an obvious move. He lit up the crowd and got us two goals, which is just what we were looking for," United manager Alex Ferguson said. Ole Gunnar Solskjaer scored his fifth league goal in the 59th, while Leighton Baines scored a penalty in injury time for Wigan. "There was a lot of elation when we heard the result from the Chelsea match, but I don't think we're going to get carried away," Ferguson said. "They maintained their work ethic and kept the passing going. There was nobody trying to overdo it and there was no showboating and that's a good sign," he added. Chelsea draw Chelsea could have kept pace with the leaders, but an own goal from Michael Essien in the 85th cost the Blues. Defender Ashley Cole cleared a cross which then deflected off Essien and past goalkeeper Hilario to make it 2-2. Didier Drogba looked to have given Chelsea the winning goal in the 72nd when he beat goalkeeper Marcus Hahnemann to head in Salomon Kalou's cross for 2-1. It was Drogba's league-leading 12th goal this season and 19th in all competitions. Earlier, Drogba gave the Blues the lead in the 38th when he out-jumped Hahnemann to head in Frank Lampard's corner. Forward Leroy Lita headed in a cross for Reading in the 67th to tie it at 1-1. "Of course we want to win every game and we are never happy to draw, but there is no criticism aimed at my players because they did the best they possibly could," Chelsea manager Jose Mourinho said. The game was played without incident after the last meeting between the clubs saw both Chelsea goalkeepers suffer head injuries. Petr Cech is still recovering from a fractured skull sustained in Chelsea's 1-0 win in October, while Carlo Cudicini - who was on the substitute's bench Tuesday - suffered a concussion. "We don't have enough cover so at this moment we are having problems," said Mourinho after revealing captain John Terry could be forced to undergo surgery on his injured back. Arsenal and Bolton are immediately below Chelsea with 36 points, Portsmouth has 35 and Liverpool 34.