A fifth-place finish in 2011/12 helped to raise expectations on Tyneside, with it hoped that another UEFA Champions League push would follow this season.
Alan Pardew has, however, been unable to replicate the heroics of last term, with Newcastle currently sat in the bottom half of the Premier League table.
A run of one win in seven has held the Magpies back, along with a crippling injury list, and Santon concedes that the players need to drag the club out of a concerning slump.
"This is the toughest time the club has been through since I've been here," said the Italian full-back.
"Last year was great, but now it's a bit more difficult. But we've got to stay positive, give a little more and try to get that win."
Newcastle will be hoping to get back on track against Southampton on Saturday, but Hatem Ben Arfa picked up a knock during Thursday's Europa League clash with Maritimo to join the injured Yohan Cabaye and suspended Fabricio Coloccini on the sidelines.
Santon added: "Hatem is really big for us and we'll miss him.
"He's been our best player this season and without him, it will be difficult. We'll have to try a different type of player because he's so hard to replace."