Did you know that Manchester United will never win the title unless they can tighten their defence and stop giving goals away? Did you know that if Luis Suárez carries on at his present rate he will end up player of the season? Weird, isn't it, how football can take what you know, or think you know, and turn it on its head?

Less than a month ago everyone was saying the same thing about United's season, at home as well as in Europe. They had to stop letting their opponents score first, for while few are better than United at chasing a game, it is not a practical gameplan to take through a whole campaign. Sir Alex Ferguson said it, Wayne Rooney said it, and Ryan Giggs said it. United could not keep giving themselves a mountain to climb.

Now United are back on top of the Premier League and through to the Champions League knockout stage with two games to spare, it seems less axiomatic to say they are playing in the wrong way. They might be giving their manager and fans palpitations, but clearly they are doing something right. United have conceded first in 10 of their 17 games this season, yet results do not appear to have suffered.

Without doubt they should tighten their defence, because in the later stages of the Champions League in particular they will come up against well-organised defences unwilling to let them back into a game in the manner of Braga or Aston Villa, yet a side that can come back 10 times by mid-November can probably repeat the trick more often than not. In the Premier League, especially, you would not back against United staying on top by carrying on just as they have been.

The reason for that is twofold. Not only do United have four of the best strikers around, with Javier Hernández so impressively rejuvenated the excellent Danny Welbeck is struggling to get a look in, but the side perform better when instructed or compelled to move the ball forward quickly. Last week in Braga, United had clearly been instructed to stay patient, keep the ball and move up the pitch slowly – and the result was painful to watch. They did not keep possession especially well, they created little or nothing in terms of attacking threat for an hour and could easily have been two or three goals down, rather than just one, by the time Robin van Persie arrived to save the day.

Van Persie's equaliser set up United for two more late goals and a 3-1 victory that flattered them enormously, and Mike Phelan claimed afterwards that the substitute's arrival allowed United to play further up the field. Never mind for now why United could not play further up the field when they just had Welbeck and Hernández up front, the point is that by Van Persie's arrival they wanted to get upfield, and Ferguson was able to select a stronger attacking combination when he needed to.

The unexpected boost to United's attacking strength this season has been the form and fitness of Hernández, who looked a little bit of a passenger last season but is now right back to his best. Van Persie has scored more goals, but Hernández has rescued United against Braga and Villa and provided what could turn out to be a crucial winner against Chelsea. "There are goals in the side again," Ferguson said, when asked whether United could still hurt the top teams in Europe. There are, and in two-leg knockout situations United are at least as likely to score as any European opponent. Conventional wisdom insists a leaky defence will find them out, but we shall see.

Conventional wisdom also has Liverpool's Suárez as a bad hat, a pantomime villain, a diver and a serial winder-up of opponents and referees. He may be all of those things but now that his season is not being clouded by the clumsily handled race row of 12 months ago, it is blindingly obvious that he is a terrific player. He has scored eight of Liverpool's 14 goals this season, some of them goals few other strikers could have managed, and as Jamie Carragher has just said with typical candour, he is not playing alongside the kind of players that Chelsea can boast.

Someone said of the 1-1 draw at Chelsea at the weekend that if the strikers had been swapped around Chelsea would have won 3-0. They might have gone on to add that without Suárez Liverpool would be in relegation trouble by now, because he is carrying the Liverpool attack to an extent that is almost embarrassing. The difference between Suárez's role at Liverpool and Van Persie's at United could hardly be more marked, and the same goes for the attacking resources each club can muster, yet the two players are joint top scorers in the Premier League.

"I've been saying for 12 months that Luis is the best player in the Premier League," Carragher told the Liverpool Echo after the Chelsea game. He would say that, wouldn't he, but maybe he is right. Suárez is outrageously talented, according to Brendan Rodgers a joy to work with and an inspirational professional, and he scores memorable goals for fun. While there were a few titters when Rodgers described him as "a breath of fresh air" a couple of weeks ago, Suárez surely deserves the benefit of the doubt. He has always been an easy player to dislike, with his histrionics, his hyperactive referee-bothering and his extraordinary and wholly original list of controversies. Yet any Liverpool player who can make Evertonians laugh, as Suárez did with his unimprovable goal celebration in front of David Moyes in the Merseyside derby, cannot be all bad.

Were Suárez playing for United or Chelsea his impact on a domestic season could be truly frightening. As it is, performing a one-man rescue mission at Liverpool he only seems to frighten the pants off Norwich, yet the class of some of his goals marks him out as a genuine contender for the end-of-season awards. Suárez is perhaps not the most clinical of goalscorers, his waste rate is quite high and he has a habit of missing easier chances than some of the ones he puts away, but if you want someone to win a game for you it would be foolish to overlook him. If there is a more watchable player in the Premier League this season you would struggle to name him. Oscar, Eden Hazard, David Silva, Hatem Ben Arfa and Van Persie are all easy on the eye, but Suárez is compulsive viewing.