Boro manager Gareth Southgate's summer rebuilding plans were thrown into turmoil yesterday when the 31-year-old Australian signed for the Magpies after rejecting a contract extension at the Riverside Stadium.

As Sam Allardyce finally got his hands on a man his predecessor Glenn Roeder had been trailing for a year, Southgate was facing the task of replacing his leading scorer, with the emotions of his club's fans in stark contrast to those of their counterparts a few miles up the A19.

Former Republic of Ireland international Slaven, brought up in Glasgow as a Celtic supporter, was hugely disappointed to see Viduka leave in a move which brought back memories for him of Roman Catholic Johnston's decision in 1989 to sign for Rangers instead of re-joining the Parkhead club from Nantes.

Slaven said: "Losing him (Viduka) would have been disappointing anyway, but losing him to our north-east rivals, as a Boro fan, I am absolutely gutted.

"I was brought up in Glasgow as a Celtic fan and the last time I felt like this was when Mo Johnston had posed with a Celtic shirt and then ended up going to Rangers.

"There was chaos in Glasgow at the time. There maybe won't be the same level of feeling at Boro, but it is hard to take when one of your top players is taken by one of your biggest rivals.

"It's bad enough losing him, but him going just up the road is gut-wrenching."

Boro insist they made Viduka an "outstanding" offer to stay put, and Slaven does not relish Southgate's task in replacing a man whose retention he believes would have been as significant as the £7million capture of Real Madrid defender Jonathan Woodgate.

He said: "Getting Woodgate was fantastic, but getting Viduka would have been just as good for me.

"He will be a big loss because he is a smashing player. He's got a presence, an exceptional first touch, he scores goals, makes goals.

"He is one hell of a player and I do not know how we are going to replace him.

"There are a lot of names being bandied about, with Jeremie Aliadiere one of them. But, as a Boro fan, Aliadiere does not excite me.

"He's not a natural goalscorer - in that respect, he could not clean Mark Viduka's boots, never mind fill them.

"Reading between the lines, Ayegbeni Yakubu is unsettled and Lee Dong-Gook hasn't scored a goal on British soil yet.

"I wouldn't want to be in Gareth's shoes at the minute.

"He has been learning the ropes after being thrown in at the deep end, and he would have hoped Viduka would have stayed put.

"That would have helped him as a young manager, but him departing makes Gareth's job a lot harder."