The forward completed a £25 million move to Liverpool last week.
The forward completed a move to Anfield last week, as the Reds paid £25 million for his services.
He is the second big name player to depart St James' Park this summer after Andros Townsend left to join Crystal Palace earlier in the transfer window.
And Colback says he believes Wijnaldum would have wanted to stay but Liverpool was too good an opportunity to turn down.
“With players like Gini, if a club come in with £25 million it will be difficult for him to stay,” he told the Chronicle.
“I am sure he would have liked to stay, but when Liverpool came in, it’s difficult. I am sure the lads wish him all the best.”
It now remains to be seen if Newcastle look to use the funds from Wijnaldum’s sale to help replace him.
He was their top goal-scorer with 11 goals last season, which is a tough surplus for the rest of the strikers to make up given how they struggled last season.
With that in mind, it would not be surprising to see Rafa Benitez look to make another addition to his forward line in the remainder of the window.