IT has taken former Hibs star Derek Riordan six long and frustrating months to establish himself in the Celtic first team.

The chances are it will not take Paul Hartley, Gordon Strachan's latest high-profile acquisition from the capital, quite so long.

Hartley's impressive debut in the 4-1 win over Livingston at Almondvale yesterday suggested there is more - much, much more - to come from him.

The former Hearts player performed with an intensity that highlighted his devotion to the club he has supported since he was a boy.

The Scotland midfielder ran tirelessly, tackled wholeheartedly, passed beautifully and tracked back selflessly for the entire 90 minutes.

There was, too, a fleeting glimpse of a bad-tempered side which has been a common component in the make-up of so many great players over the years.

Shortly after the hosts had taken a shock lead courtesy of a Dave Mackay header the red mist descended and he clattered Allan Walker needlessly.

Given he was only introduced to his new team-mates in training on Thursday morning, his performance was nothing short of remarkable.

Things will surely only get better for a talented individual who is still known to friends in his native Hamilton by his childhood nickname of Zico.

It was Riordan, his one-time adversary at Hibs, who stole the glory by netting a well-taken double that took his tally to five goals in six games.

He has staked a strong claim for a regular start alongside Jan Vennegoor of Hesselink ahead of Craig Beattie, Kenny Miller and Maciej Zurawski.

Yet, the contribution of Hartley was just as important, probably even more so, for the immediate and long-term future of the Parkhead club.

Strachan was keen to snap up the 30-year-old so he could inject some much-needed pace and penetration to a midfield distinctly lacking in those qualities.

Excellent players though Neil Lennon and Thomas Gravesen are, neither man is ever going to come first in a 100-metre sprint.

For all his undoubted ability, even Shunsuke Nakamura, who set up two of his side's goals yesterday, lacks the directness of his new team-mate.

And as for Jiri Jarosik? Quite what the big Czech Republic star contributes to the Celtic cause still remains something of a mystery.

Hartley adds a vital extra dimension to a team that has won few plaudits for the football they have played this season despite all their achievements.

As does Vennegoor of Hesselink. With his team trailing by a goal, the big Dutch hitman's ability in the air in 30 minutes proved crucial to the outcome.

He rose and nodded a Paul Telfer cross into the box down to Darren O'Dea and the young Irish defender volleyed spectacularly past Colin Stewart.

It was route one football. It was, though, precisely what Strachan's side needed in the circumstances. The equaliser visibly raised the visitors' spirits.

Riordan, who had endured a poor first half-hour against First Division opponents raising their game for the televised clash, certainly came to life.

He gratefully accepted Lee Naylor's pass and fired an inch-perfect left-foot shot into the top right hand corner of the Livi net just before half-time.

It was one-way traffic after the break. Riordan had soon bagged his second and Vennegoor of Hesselink finished brilliantly to complete an enormously satisfying afternoon for Celtic.

Celtic's reward for their endeavours is a nasty trip to play Inverness Caley in the quarter-finals at the end of the month.

That showdown will come just days after their first Champions League encounter with Italian giants AC Milan in Glasgow.

That sort of schedule proved fatal back in 2003 when, just days after they had beaten Liverpool at Anfield in the Uefa Cup, the Hoops crashed out of the Scottish Cup against the Highlanders.

However, on this sort of form, and with Rangers and Hearts out of the competition, Celtic are looking strong contenders for the silverware. Need to Know

Was it a good game?

A great deal for Celtic fans to savour after surviving an early scare. Who was Celtic's best player?

Derek Riordan's two goals just edged him ahead of debutant Paul Hartley and Shunsuke Nakamura. And Livingston's top man?

Lee Makel set up his side's goal and caused Celtic a lot of problems. What about the referee?

Charlie Richmond didn't have too many difficult decisions to make. Who's up next?

Fellow Scottish Cup quarter-finalists Hibernian at Parkhead on Saturday.