Ki picked up a knee injury following Newcastle's 3-2 defeat against Liverpool at St. James' Park which leaves the South Korean international unavailable for the trip to face the Cottagers.
United lie in 14th place on 42 points, three adrift of Bournemouth and, with a healthier goal difference compared to the Cherries, Benítez admitted his squad will target a strong finish to their top flight campaign.
Benítez said: “We have more or less the same problems that we had before. The kind of injuries they have, they will not be ready. We have also lost Ki, who has a knee problem. It is not very serious but we don’t want to take the risk.
"We have one game to play and we have to try to do well. We can finish one position higher in the table and we will try to do that.
"It will not be an easy game but you still have to be fair with the professionals who have been working so hard for the whole season. We have to approach the game with the same mentality and try to win.
“I have the same feeling as when we played against Liverpool – we are professionals and we will try to do our best. (At the end of the season), when you have players with little knocks, you don’t want to take risks with them.
A victory in West London will see Benítez's squad overpass their points tally sustained last term - with the Magpies ending in tenth pace.
Although United will not claim a spot in the Premier League's top half this season, the Spaniard believes his side have performed well after failing to win their opening ten league fixtures.
Benítez added: "You can be lucky one year but, to be consistent, you need to have everything in place. Brighton, Huddersfield and ourselves were promoted and we were more or less there but when you have Wolves and Fulham spending £100 million, it can be totally different.
“Last year, with 44 points, we finished tenth. This year, tenth place have 50 points already. That means that this year has been more difficult. Last summer, everybody was spending big money. To be where we are now is a great achievement. It may not be as big as last season but it was more difficult for sure."
