The 31-year-old Australian this afternoon signed for derby rivals Newcastle after rejecting a new deal on Teesside.

Boro boss Gareth Southgate had been desperate to retain Viduka's services as the final year of his existing contract ran down, but now faces the task of replacing last season's leading scorer.

But Lamb insists his club could have done little more to persuade Viduka to stay.

He said: "We made Mark what we consider to have been an outstanding offer to stay with us.

"Of course, we are disappointed he didn't accept that offer, but we understand that Mark felt he needed a fresh challenge.

"We wish him and his family well in the future."

Southgate will now look for a replacement, and while he knows that will be intensely difficult, he is confident he will find the right man.

He said: "We have to move on as a club. We have had to replace outstanding players in the past and we have always managed to do it.

"We may have to play in a different style and we may have different strengths to the team.

"We have to look to the future. Now is an opportunity for somebody else to step in and fill his shoes."

Southgate has been trailing Arsenal's Jeremie Aliadiere and West Brom's Diomansy Kamara for some time knowing that Viduka might leave, but while he knows life must go on, he admits his side will miss the Australian.

He told the club's official website, www.mfc.co.uk: "It is a regret for me, but we did everything we could as a club to try and keep him.

"The fact that he was in the latter months of his contract was difficult. It meant he was able to speak to other people, but there was nothing more from that period on that we could have done.

"We made him an excellent offer, but sometimes players feel they need a new challenge and something different.

"We missed him when he was out with broken foot and then from Christmas on, he was a real talisman for us.

"There were some afternoons when he was almost unplayable for the opposition."