Getting game here won't be easy...it's just as well I'm a hard grafter

It's understandable, therefore, that the challenge for which he has signed up at Celtic is not one which fazes him.

The New Zealand striker has overcome greater hurdles than breaking into the Parkhead first team, the most recent of which was the snapped Achilles which kept him out of action for the second half of this season.

So, the warning has been well and truly delivered to the other strikers at the club that Gordon Strachan has recruited one of the most determined and single-minded players in the game.

Killen may not be the blue chip' player the champions' fans are eagerly anticipating, and the Bosman signing cost £4.4million less than Scott Brown, who he followed along the now well-trodden path from Easter Road to Parkhead.

But the value the 25-year-old brings to the side will soon become clear, and it comes right from the core of his being.

Killen meets every challenge head on, and will let nothing stand between him and his goal.

As he revealed, that was an essential quality when he arrived on these shores eight years ago.

"I left home at 17 with a one-way ticket and £500 in my pocket," he said. "That's as big a challenge as any you will face.

"I came over from New Zealand on a two-week trial at Manchester City and just worked my way from that point.

"So coming to such a massive club with massive expectation is something I am going to relish.

"I'm not here just to make up the numbers. I've come to play and I'm coming in with my eyes open as everyone told me there was this player, that player and other players already here who can play up front.

"But that's just another challenge I'm happy to accept. I've always been a grafter, a hard worker and it's never been a problem to me putting in the extra hours to improve.

"That's the way I am and that's how I'll continue to be.

"Sometimes you take a path and things don't go the way you want, then it is time to move on. I hope I'm taking a forward step here. I'm sure I am because I want to push on with my career."

Killen has graduated from the football academy of hard knocks, his three substitute appearances for City failing to open the door to a career there and eventually leading to him going on loan to Wrexham and Port Vale, before he was signed by Oldham for £250,000.

Anyone who knows how unpleasant a cold winter's night at Boundary Park can be will understand why it came as something of a relief to get the chance to join Hibs, albeit the fact Oldham were struggling to find the funds for his wages at the time helped the move to go through.

Despite reports the fee paid was around £200,000, zero would be nearer the mark. Which makes the contribution Killen - who scored his first goal in is second game for the club, against Rangers - made to Hibs in the 18 months he was there all the more impressive.

It also makes the fact they were only prepared to offer the Kiwi cap a 12-month contract when his first deal was due to run out at the end of this season all the more surprising.

The serious injury sustained in the final minute of Hibs' cup tie at Pittodrie back in January might have had something to do with their reluctance to commit.

But with others - including Cardiff and Southampton - willing to snap him up, Killen has never had cause to doubt himself.

And when Celtic made their move at the 11th hour, the die was cast - he was going to bring his talents to Parkhead.

Although considered by many to have been recruited as back-up for Jan Vennegoor of Hesselink, Killen reckons he has much more to offer - and, in typical determined fashion, he aims to prove the point.

He said: "I don't like to think of myself as just a hold-up player. I like to get stuck in and have a battle."

Killen's aggressive approach makes him a very different player rom target man Vennegoor, and he brings a physical presence which Strachan has been seeking to add to his attack for some time.

Killen acknowledged: "I'm not afraid to stick my head in and put my foot in and work opponents hard."