Advocaat was drafted in to help the Black Cats avoid relegation after Gus Poyet's sacking and, despite losing his only game so far, at West Ham, Scotland striker Fletcher is upbeat about the run-in.
The club lie just a point and a place above the bottom three with eight matches to go, but Advocaat has already made an impact.
"It's been really lively since the new coach has come in; he's a lively character and he's brought that into the training sessions," Fletcher told safc.com.
"He wants us all to give 100 per cent and believes we've got the quality to turn our fortunes around and push up the league.
"He wants us to play a lot more compact and push forward as a unit, and I think we did that in the last game because we won balls back and created chances.
"We've got to remain upbeat and stick to the task at hand."
Despite their struggles at the helm, both Poyet and his predecessor Paolo Di Canio enjoyed early success against Tyne-Wear rivals Newcastle, and Advocaat has his own opportunity after the international break
"There's no better game to turn things around in than the derby," added Fletcher.
"It's a great first home game for the new coach, so we're all looking forward to it."
Source : PA
Source: PA