Victory against Sale Sharks on Friday night would see Gloucester climb into third spot above Harlequins and Northampton, who have fixtures against Bath and London Welsh, respectively, this weekend. Quins, Saints and Gloucester are currently separated by just two points.
"The table is so congested that fourth spot could go to anyone at the minute," said Sharples, who is on the Gloucester bench at Salford City Stadium. "We have three games left, two of which are tough away games, but we have every chance of making it."
He added: "I think if we win our last three games we have to have a good chance. We would certainly put ourselves in a good position.
"We have to look at it as knock-out rugby now. We are desperate to get into that top four. If we lose points now, someone else will take them and move ahead.
"You couldn't really call it in that top five at the moment. There's still a lot to play for, it's going to be a massive push for a top-four spot."
Gloucester rugby director Nigel Davies has made five changes from the team beaten by Amlin Challenge Cup quarter-final opponents Biarritz last Thursday, with full-back Rob Cook, wing Shane Monahan, centre Billy Twelvetrees, scrum-half Dan Robson and hooker Huia Edmonds all starting.
And there is a spot among the replacements for England number eight Ben Morgan, who is poised for his comeback after being injured during this season's RBS 6 Nations Championship.
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