And then there were six.

Or, if you live in the south-west of Ireland and take a more melancholic view of life, just five. But regardless of whether Munster are still in the running or not, there is no question whatsoever that the race for the RaboDirect PRO12 title is already shaping up to be the most enthralling in years.

That much was guaranteed by the most recent round of games. The weekend's critical matches began with Glasgow's sensational 51-24 thrashing of Munster at Scotstoun, a result that reverberated around the four PRO12 nations, proclaiming Gregor Townsend's side to be genuine title contenders.

The following day, the Scarlets of Llanelli edged a tense away encounter in their Welsh derby against the Dragons, albeit without a bonus point in their 28-20 win. Then the Ospreys kept themselves in the hunt with a 23-16 success against the Blues in the second part of the Millennium Stadium double-header, although they also had to live without the bonus point that would have strengthened their top-four position.

The final match that mattered was at the Royal Dublin Society Ground, where Leinster, tails up on a ground where they had not lost all season, were expected to beat Ulster with something to spare. Leinster were coming on to a game, while Ulster, beaten by Edinburgh eight days earlier, seemed to be going off the boil. But again all expectations were blown to smithereens as the men from the north, inspired by another brilliant display by Ruan Pienaar, turned the form book on its head and clinched a remarkable 22-18 win.

As a consequence, Glasgow ended the weekend at the top of the PRO12 table, with 67 points. And deservedly so. Townsend's team might have had a fortunate fixture schedule early in the season, but after a mid-campaign wobble they have demonstrated their championship credentials time and again. Only Leinster have scored more points than the Warriors this season; only Ospreys have conceded fewer. With three games remaining, they have already claimed eight bonus points, more than any side since Scarlets six years ago.

But the final straight is a fiendishly tough finish. Nine points ahead of Ospreys and Scarlets, level on 58, and 20 better off than Munster, it would take a major meltdown for Glasgow to miss out on a place in the top four now, but the real prize to be grasped is one of those precious places in the top two. With that comes a home semi-final, the importance of which is underscored by what has happened over the past three seasons.

There have been six semi-finals since play-offs were introduced for the 2009/10 season. Of those, not one has been won by the away team. Having twice finished up on the losing side at that stage, Glasgow's players bear the scars of past competitions – and a determination that they will be fighting for a place in the final on home soil if humanly possible.

There is a premium, too, on finishing top of the pile. According to league rules, of the two finalists "the team that finished highest in the league stage [....] will be able to propose a venue within its own Union's jurisdiction [which may include the team's own ground] to host the RaboDirect PRO12 final." The rules also state that the ground which hosts the final must have a capacity of at least 18,000, but the indications are that some flexibility would be shown if Glasgow nominated Scotstoun, which falls short of that number even with temporary stands in place.

So how are the runners and riders shaping up? To an extent, although probably a smaller extent than in recent seasons, the results of the past few months have been distorted by Six Nations considerations. It is impossible to overlook the fact that some of Glasgow's most significant players – Josh Strauss, Niko Matawalu and DTH Van der Merwe spring to mind – have not had that distraction. But then, the supposition that Leinster's performances and results had been depressed by the absence of a raft of Ireland players was not exactly borne out by their loss to Ulster when they had all those players back in their side.

As in all the best competitions, every team in that top group has the ability to beat every other team on its day. A sensational month of PRO12 rugby lies in store.

The race might not be to the swift nor the battle to the strong. Keeping nerves in check might matter most of all.

GLASGOW

Position: 1st. Points 67.

The Warriors have been the surprise package of the season. It was expected that they would take time to settle after Gregor Townsend displaced Sean Lineen as head coach, but they hit the ground running and overcame a mid-season dip to harvest a stack of league points and bonus points in the new year. Glasgow were unlucky not to take a stranglehold in the competition when they were edged out buy Leinster in Dublin the weekend before last, but they bounced back superbly to thrash Munster at Scotstoun six days later.

Remaining games: April 12, Scarlets (a); April 19, Ospreys (h); May 3, Connacht (a).

ULSTER

Position 2nd. Points 66.

The Ravenhill side seemed to be running away with things earlier in the season, launching themselves into the new campaign with 11 straight victories before losing away to Munster in their last match of 2012. They had a difficult time of it during the Six Nations, however, and they have been beaten by Ospreys, Glasgow and Edinburgh over the past few weeks. They found themselves brilliantly in their away win against Leinster last weekend, but the distraction of the Heineken Cup could count against them if they can squeeze past Saracens in their quarter-final this weekend.

Remaining games: April12, Dragons (h); April 19, Connacht (a); May 3, Blues (h).

LEINSTER

Position 3rd. Points 64.

The Dubliners established themselves as the greatest team of the age when they won their third Heineken Cup in four seasons last year, but they have been curiously inconsistent during this campaign. On their day, and with their star names all firing, they are still a force of nature, but they have been blighted by injuries. However, Ian Madigan, who beat Glasgow almost single-handedly, has emerged as a more than able deputy for Jonny Sexton, and is exerting huge influence just now. Like Ulster, though, they have a European distraction, and may be fired up by the prospect of playing an Amlin Cup final on home soil.

Remaining games: April 13, Munster (a); April 21, Zebre (a); May 3 Ospreys (h).

OSPREYS

Position 4th. Points 58.

The reigning PRO12 champions got off to a horrible start to the new season, losing their first three games. They were also beaten by Edinburgh in November and only just squeezed past struggling Zebre in their first game of the new year. They also had a bad wobble when they lost to Connacht in February, but that was before their big guns came back from Wales' triumphant Six Nations campaign. Their pack is formidable and they have given away a measly 16 tries this season, 10 fewer than the next best defensive side. Hitting their stride at just the right moment, but they have a tough run-in, finishing with a potentially cataclysmic clash with Leinster in Dublin.

Remaining games: April 13, Treviso (h); April 19, Glasgow (a), May 3, Leinster (a).

SCARLETS

Position 5th. Points 58.

The men from west Wales have rather crept under the radar screen this season, putting together a decent sequence of results without causing any great excitement inb the competition at large. They did start with a good run of three wins, including an impressive 45-20 victory over Leinster on the season's opening weekend, but everything has been rather stealthy since. George North gets most of their headlines, bufor the most part they are a team of workers rather than stars. Still, they have the most advantageous draw of all the sides chasing play-off places, with three home games, only one of which is against a fellow contender.

Remaining games: April 12, Glasgow (h); April 20, Blues (h); May 3, Treviso (h).

MUNSTER

Position 6th. Points 47.

It has been a hugely disappointing season for new coach Rob Penney. The New Zealander advertised his intention to widen Munster's forward-oriented game, but the men from the south-west of Ireland seem to be caught between two styles of play at the moment. Having lost a host of big names last summer, they have also had to live without their talismanic captain Paul O'Connell for most of the season. They will be fired up for their home clash with Leinster, but even with reasonably easy fixtures against Dragons and Zebre to follow it is hard to see them getting through.

Remaining games: April 13, Leinster (h); April 19, Dragons (a); May 3, Zebre (a).