The stakes were high, the pressure intense and the atmosphere incandescent. Thousands of fans transformed the National Stadium into a cauldron of colour and noise on Sunday afternoon as Valletta, the hot favourites for the league crown, ran into Birkirkara, the leaders of the Premier League whose inexorable march has spiced up the title race.

Although Birkirkara went into Sunday's skirmish with a one-point lead at the top, Valletta were still backed by many to re-assert their status as leading contenders for the title but, not for the first time this season, City's 'stars' failed to deliver.

Tactical cohesion, an excellent work ethic and good counter-attacking play, the hallmarks of Birkirkara's consistent run this season, came to the fore on Sunday as Paul Zammit's men rolled up their sleeves and quelled Valletta's renowned flair with their committed and disciplined approach.

With Paul Fenech and Sylvano Comvalius, two first-choice players, both succumbing to injury inside the opening 24 minutes, Birkirkara will have been entitled to think that the footballing gods had turned against them but Trevor Cilia's 19th minute breakthrough galvanised their resolve to defy the odds.

And that is exactly what the Stripes did as they dug in to defend their slim lead and secure a victory that significantly bolsters their chances of winning the title, given that they are now four points clear of Valletta with only five matches remaining.

At the final whistle, a tearful Zammit pointed to the sky to salute his late mother before being mobbed by technical staff and players amid the joyous cheers of the Birkirkara fans.

There was no disputing the significance of Birkirkara's win but typically, Zammit preached a mantra of caution after the match.

"All the attention had been on Valletta because they have invested heavily in high-profile players this season," Zammit said at the post-match news conference.

"We worked a lot on tactics ahead of this match and our efforts have paid off. It was a very tough encounter, full of episodes. I had to make two substitutions in the first few minutes but we kept going.

"This is what the squad is all about and this is what really gives me a good feeling about my work. It was pleasing to see the substitutes (Alan Tabone and Joseph Zerafa) go in and do an excellent job for the team.

"Although we now have a four-point lead at the top, the war is not over as a series of tough battles lie ahead."

Sunday's victory sets Birkirkara up nicely for their FA Trophy quarter-final against Valletta on Saturday and the Premier League clash with Sliema Wanderers the week after.

"This game marked the start of a two-week period during which we have other important games against Valletta in the FA Trophy and Sliema Wanderers in the league," Zammit said.

"We prepare for one game at a time. This has been our approach since the start of the season. Obviously, these kind of matches generate more interest because they are like cup ties."

Rowen Muscat, named man of the match on Sunday, has come to epitomise Birkirkara's rapid rise as he has established himself as a key figure in their midfield.

"I've always admired Rowen Muscat," Zammit said. "Even when I was coaching Valletta, I knew that Birkirkara had a very talented player in Rowen Muscat. The potential has always been there."

For months, Zammit has been mindful not to augment pressure on his players by talking up Birkirkara's title chances but victory over Valletta left no-one in doubt about their lofty aspirations.

"We can't say that we're not interested in winning the league, especially now that we are four points clear, but the title issue is still open," Zammit said.

"Let's not forget what happened last year. In the first round of the Championship Pool, we were six points behind Hibs but we managed to turn the deficit into a one-point lead, only to lose everything in the last two matches."

Valletta coach Ton Caanen acknowledged that his team ran out of ideas during Sunday's match.

"We didn't play good football," Caanen said.

"It was a tactical match and Birkirkara played a waiting game. We just couldn't penetrate their defence. Our midweek game against Tarxien (Anniversary Cup semi-final) is no excuse for our performance against Birkirkara. We're a professional team and we had sufficient time to recover.

"It was not our day. If one or two players from your team perform badly, you can change things by making substitutions but, as a team, we didn't come into the game. Birkirkara have the two best centre-backs in the league when it comes to stopping attacks.

"We played too many unnecessary long balls and 15 times during the game I urged my players to try and build up play through the middle but the midfielders were too far from the defenders.

"Although Birkirkara played well, I think that both teams deserved a point. Birkirkara's goal came after an unfortunate mistake by Steve Bezzina who didn't clear the ball away for a corner. We ran out of luck but the game is over now.

"Now the most important thing is how you respond to this setback. There's still five games to go in the league and we also have a cup final (Anniversary Cup) and FA Trophy quarter-final to look forward to.

"In difficult times, we must stick together. Our motto is one aim, one unit and this how we will try to react to this defeat. I also hope the fans stay behind the team but I know that after such a defeat, it's not easy to control one's emotions."

Caanen openly criticised the format of the Premier League when answering a question about Valletta's title chances.

"I would say that Birkirkara now have a 75 per cent chance of winning the league," Caanen claimed.

"We now have to see what happens in other games but for me, these play-offs (Championship Pool) make no sense.

"Birkirkara and Valletta, and maybe Sliema, deserve to be involved in proper games, not friendlies but because of this format, three or four teams have little to play for in the final weeks of the season.

"Last week, Tarxien produced a strong performance against Birkirkara but sometimes, it's difficult to motivate players when they have no objectives to fight for.

"I hope the other teams give their best in the remaining matches. Personally, I feel that we still have a chance in the league, so let's move on."