But while he is expecting Fortune, Jonny Evans and the other new signings to give the club a real lift in the days ahead, he says no-one should forget that it's the players already at the club who will carry most of the burden of keeping the club in the top flight this season.
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"We're hoping to bring in three or four new players in January.
"But that's a big if and the defeat at Wigan in the cup certainly doesn't help.
"I expect our targets will be asking for more money after seeing that result!
"We've lost lots of games this season and it's not good enough so we have to look at how to change that.
"I sound like an old record player now but for me it comes down to working harder and looking to bring one or two players in.
"But we can't simply rely on any of the new players that come in.
"The players we have are still going to be the nucleus of what we hope will be a successful Premiership season.
"We will bring two or three players in who we hope will bring a bit of quality and strength but it's down to the players who we've got to start picking up the points the squad will be capable of."
Thirty-year-old Fortune has been training with Sunderland for the last month as he makes his way back to full fitness following an operation.
The South African midfielder, a former team-mate of Keane's at Manchester United, was released by Bolton Wanderers last summer and is expected to join the club in the next few days.
Keane said: "Quinton's been building his fitness up while he's been here and he's done well.
"A move should go through next week but there's no rush."
Fortune will be the second player with Manchester United links signed by Sunderland this month - last Friday Jonny Evans arrived on loan until the end of the season last Friday.
Evans was outstanding in the heart of the Black Cats defence while on loan last season but at the weekend he blotted his copybook when he was at fault for Wigan's second in the 3--0 defeat.
Keane said: "I thought Jonny did alright - he's a young man and we can't too much pressure on him.
"He did reasonably well considering he's not played many games of late but he'll be disappointed with that goal because he's a better player than that."
As well as the new signings, Keane will be looking towards players coming back from injury.
The valuable Carlos Edwards continues his rehabilitation from a broken leg while Nyron Nosworthy got a run-out at the weekend - his first game since November though he was clearly ring-rusty.
Keane said: "Players coming back will be important.
"Nyron has trained for a couple of weeks so we felt confident in starting him.
"Ideally we wouldn't have asked him to play 90 minutes but there's no doubt that that 90 minutes will have done him good and put him more in the picture for the game coming up against Portsmouth next weekend."
Many players have been linked with Sunderland over the last few weeks but the names that crop up most frequently are Portsmouth's Matt Taylor, Reading's Leroy Lita and Steve Hunt, Blackburn Rovers' Robbie Savage and Chelsea's Steve Sidwell.
