Ireland v Australia: One steps out, but two step in as recognition of Ulster's rejuvenation under Mark McCall and Allen Clarke continues apace.

While the fickle hand of hamstring tweaks has interrupted Andrew Trimble's upwardly mobile Test graph at a point when he has never looked more at ease, his provincial team-mates, Isaac Boss and Bryan Young, will make their first Irish starts against Australia on Sunday.

In one further change to the team which beat South Africa, Geordan Murphy returns at fullback in place of Girvan Dempsey, in what is effectively the third of what can be interpreted as a rare excursion by Eddie O'Sullivan into that unmentional terrain of "rotation". The Irish coach explained he wanted to "have a look at Geordan to see what kind of form he's in at fullback" having played this season on the wing for Leicester and admitted Dempsey was a little unlucky.

Having fallen a little out of favour, this is a massive opportunity for Murphy and Denis Hickie, not to mention Boss and Young. "I'm happy with this team. It's not unduly weakened by the changes. A couple of opportunities for guys who are maybe less than experienced, a couple of opportunities for guys who are very experienced. It's about building the squad", said O'Sullivan.

"So it's a work in progress, as we said at the outset. It's not over the top, but at the same time it's a team that can go out and win a Test match."

With Hickie recalled for his first start since the Millennium Stadium two seasons ago, the net result of this is that the one-time Dream Team in the back five - Dempsey, Hickie, Gordon D'Arcy, Brian O'Driscoll and Shane Horgan - are in harness for only the second time ever.

To O'Sullivan's immense frustration, injuries prevented him from playing this quintet in unison until the Six Nations opener in Rome two seasons ago, and then it only lasted 33 minutes before D'Arcy succumbed to a torn hamstring which sidelined him for the rest of the season.

It's perhaps a testimony to the subsequent emergence of Trimble (O'Sullivan said they were "just being sensible" about a hamstring which has developed a tendency to tighten up, but might see him back the following week) and the rejuvenation in Girvan Dempsey's form with Leinster, that O'Sullivan's decision to re-unite this quintet has virtually gone undetected.

It's also ironic that when they finally do come back together, the Irish team has sacrificed the rapid-fire, silver-salver service of Peter Stringer in a frontline international for only the second time in almost seven years.

The first occasion, in the re-arranged foot-and-mouth match of September 2001 against Scotland at Murrayfield, was a costly experiment. Otherwise, Stringer has started in 67 of Ireland's last 77 Test matches, and the remaining exceptions were decidedly B list, v USA (twice), Fiji, Tonga, Samoa, Italy (in a 2003 World Cup warm-up match at Thomond Park), Japan (twice) and Romania last year.

The 26-year-old Boss, born and reared in Tokorua, New Zealand, where he learned the game with his local club, Southern United, south of Hamilton, came through the ranks at Waikato and moved to Ulster in October last year, having been tapped up by Clarke a year previously when the Ulster assistant coach had been alerted to Boss's eligibility.

The link had been established by Andy Ward - Boss also having played briefly with Ward's club Hautapu, as Boss qualifies by dint of a maternal Irish grandmother from Glenarm, Co Antrim.

"He's a different player than Peter," ventured O'Sullivan. "I suppose he is a more robust player in some ways in that he's more aggressive around the fringes. He likes to run a lot and take on the backrows at scrums, he likes to take on the Pillar A defender, and he's the kind of guy who can create problems in that area."

Not as quick a pass as Stringer, but more of a sniping presence allied to a very good box kick, his decision making has improved under the guidance of the Ulster coaches and more specialist one-on-one coaching here. "Definitely. I've had a lot of advice and help from Stephen Aboud (IRFU director of elite coaching and a former scrumhalf). That's been great for my game."

Winning his fourth cap, this will be his first start after replacement cameos against New Zealand and Australia in the summer, and last Sunday against South Africa.

Similarly, the 25-year-old Young will be making his first start after three brief appearances in the same games.

From the same alma mater as David Humphreys and Matt McCullough - Ballymena Academy - Young came through the age-grade ranks within Ulster, captaining the province and Irish schools (in 1999) and Ulster and Irish under-21 sides in 2001. His big break came last season when Justin Fitzpatrick was injured and Young went in at loosehead and hasn't looked back. Tony D'Arcy, the one-time Ballymena and Irish forwards coach, has been a major influence and has always predicted a big future for him.

Although O'Sullivan welcomed Ulster's decision to broaden Young's experience at tighthead this season, there's little doubt he's much more comfortable at loosehead, where he starts, for the first time this season, in place of Marcus Horan.

While the starting team's combined haul is relatively reduced, a vastly experienced bench boasts 335 caps.

The speculation is the Wallabies might revert Stephen Larkham to outhalf and unite Lote Tuqiri at outside centre with the hugely influential Stirling Mortlock in midfield, and recall Mark Gerrard, a double try scorer in their 30-14 win at Lansdowne Road a year ago. It would also more closely resemble the back line which cut Ireland apart in last June's 37-15 win in Perth, although apparently Australian assistant coach Scott Johnson would prefer to keep Mat Rogers at 10 and Larkham at 12.

Anticipating a much tougher game than last Saturday's, Brian O'Driscoll echoed O'Sullivan's comments about the smarter Australian drift defensive system luring opponents into space before closing it off. He's also revised his opinion about Ireland's defensive effort against South Africa. "With . . . hindsight and having looked at the video we were guilty of some very poor defensive decision making and some bad missed tackles. We need to make sure we put that right against a smarter team like Australia because they'll punish you for mistakes like that."

In short, Ireland need to be smarter all round.