What do Liverpool, Fulham, Aston Villa, FC Porto and Sunderland all have in common? They’ve all scored on Manchester United within the last month.

The champions boasted a staggering number of clean sheets this season, but in recent contests, as the aforementioned sides have proven: if you attack Man U you can break down their defenses and score.

While only Liverpool and Fulham have enjoyed wins, Villa and Sunderland looked perfectly capable of stripping points off United and Porto’s two away goals will give them the confidence to chase victory in the upcoming Champions League match.

The window for taking points from United in the EPL is ever closing with seven matches to play and perhaps the best chance already squandered (Villa’s visit to Old Trafford while Rooney, Scholes and Vidic were all suspended,) but United’s remaining adversaries can take a lesson from the goals conceded: attack, attack, attack.

United have enjoyed many close wins this season, and their 1-0 victories in particular often came from United repeatedly hammering away at a defense-minded side until the deciding goal went in, but since Liverpool scored four goals at Old Trafford on 14 March followed by Fulham’s 2-0 upset the following weekend, Sir Alex Ferguson’s giants have shown they have chinks in their armor.

When Liverpool and Fulham took the game to United and pressed into the attacking third, the champs made mistakes and lost the points. Villa looked the better team by far when they visited Old Trafford on 5 April, but Ronaldo’s second goal gave United a massive lift and they were able to recover and win the match with a stoppage time goal from 17-year old Federico Macheda on his debut. Sunderland also looked perfectly capable with a fantastic equalizer and many brave forays into the attacking third for the rest of the match, but a second United goal was enough to secure the points.

But the clean sheets are gone and opposing sides can see that damage can be done. The question is: is there enough time left to take the points needed for Liverpool or Chelsea to overtake the champs?

Vidic’s suspension and Ferdinand’s injury woes have certainly aided in United conceding goals, but I would argue that United have enjoyed a stigma of being unbeatable for much of the season, encouraging sides to sit back and hope for a point, too often resulting in disappointment. This stigma has since evaporated and Man U’s opponents see the value in chasing the win.

Sunderland looked capable of producing a draw and Villa looked more than capable of a win. While United only needed a small spark to dash the hopes of both clubs, they couldn’t produce this spark against Fulham or Liverpool or prevent Porto from securing two away goals.

While nobody, including myself, will be surprised if United clinch the title once again, I see plenty of room for upset in the remaining matches. Portsmouth, Hull and Boro all have something to fight for. Spurs, City, Arsenal and perhaps even Wigan have shown enough good form feel up to the task.

United are not invincible. Their weaknesses have begun to show. The upcoming fixtures will be telling, but if sides keep attacking, we may continue to enjoy a two- or three-way title race until the very end. We shall see.