Colback - who was made available for transfer in the summer - has been training with the club's development squad since August.
Saivet was an unused substitute at Turf Moor however, with Merino and fellow Magpies midfielder Isaac Hayden struggling to return to full fitness for the weekend, the Senaglese midfielder could be afforded a rare opportunity to rove his value to Benitez.
Cook struck two minutes into injury time to give Eddie Howe's team only its third league win.
"I will not talk about the decisions because I am not very happy with the decisions", Benitez said in his press conference, having told Sky Sports earlier: "I think we lost, that's it, and we'll have to analyse". He knows the situation.
Salah fires Liverpool to pile pressure on Bilic
Whilst a home victory would lift the pressure off West Ham's Bilic, Reds' boss Jurgen Klopp may have a few uncomfortable questions to answer to.
"No. We are thinking about correcting the things that we haven't done well, and we have a couple of weeks to keep working and trying to do our best".
It's FAI Cup final weekend so FAI Cup victor and St. Pats midfielder, Conan Byrne will be this week's guest in the Boot Room as we look back on the Saints successful cup run of 2014. We didn't want to have six.
The Premier League takes a break for worldwide games after this weekend so I always feel it must be even tougher to stomach a defeat when you know you'll have to wait an extra week to play again.
The Magpies are now ninth in the league standings and they have performed particularly well at St James' Park of late, winning three and drawing one of their last four top-flight games on home soil.