Ugo Monye is happy to spearhead Harlequins' bid to defeat London Irish and reach the Guinness Premiership final, despite the ever-present threat of injury ending his participation in this summer's Lions tour.

With Munster's Tomas O'Leary already ruled out by a broken ankle and Cardiff's Tom Shanklin dislocating a shoulder on Wednesday night, the Lions are preparing to make two changes to their original tour squad for South Africa, highlighting the dangers lurking in every remaining game of the season.

If Quins can emerge victorious in this outstanding semi-final clash with Irish tomorrow, they would meet either Bath or Leicester at Twickenham on 16 May and Monye's blistering pace is going to be a key weapon.

Irish have their own world-class speedsters in England internationals Delon Armitage, Topsy Ojo and Samoa's Sailosi Tagicakibau but Monye is the quickest of the lot.

Monye (below), who ran the 100 metres in 10.6 seconds as a teenager and will be the fastest Lion in Africa, said: "You do let your mind wander at times and think about the tour to South Africa but these big games ensure my focus comes right back to helping Quins.

"Of course, what happened to Tomas O'Leary is a tragedy but I don't think about getting injured and I will be giving 100 per cent in the remaining Premiership games.

"I am a strong believer in what will be, will be and everything happens for a reason and I won't be holding anything back for the Lions tour. I will be going hell for leather.

"Playing well for the club would be a great way to leave on tour and, hopefully, I will have the Premiership title in my back pocket."

Monye, having played alongside full-back Armitage in his six England caps to date, is keenly aware of the threat posed by an Irish side that also base their multi-phase attacking rugby on a tireless defence.

Turnovers are the lifeblood of both back divisions, with flanker Will Skinner, the Quins captain, and Steffon Armitage, his Irish opposite number, having crucial roles to play in securing loose ball.

It all adds up to a strength-sapping match and Monye said: "This could be the quickest match of the season. With both teams happy to express themselves with the ball in hand, the tempo is going to be high.

"They have a great back three with lots of speed and have played well all season and if we turn up and play to our potential, then this is going to be a great game.

"The main lesson we learnt in the defeat by Leinster in the Heineken Cup is about the need to take every chance in big games like that and we made three or four clear line breaks and didn't nail the try.

"That was really disappointing against a very good defensive unit and Irish will be different because they have a particular way of defending which we have to counter. We have put that quarter-final defeat behind us and are aiming to produce the performance that beat Stade Francais twice.

"We have a lot of English guys in our team who share the same mindset and that's also the case when we play for England. We want to achieve great things and I don't know if you would find a team unity to match what we have at this club.

"We have come a long way from being relegated from the top flight, getting straight back up and to now be one game away from the final is hugely exciting.

"It does seem a long way from playing Otley in the First Division to taking on London Irish in the Premiership semi-final and we have done that in great style by scoring tries. The days of sticking the ball up you jumper and keeping the ball in the forwards have long gone and now it's about using all 15 men on the field and producing exciting rugby.

"It sounds like a bit of a fairytale story to be playing at Pertemps Bees four years ago and then this season playing in front of 75,000 in Paris and beating Stade Francais but it did happen."

Irish have Peter Hewat at outside-half, with veteran Mike Catt ready to enter the fray from the bench, while young Adam Thompstone, the highly-rated back, has been chosen ahead of England wing Ojo to highlight the attacking talent available to the Exiles.

Guinness is thanking Harlequins and London Irish fans tomorrow with a £2.50 pint offer in honour of its 250th anniversary.