if the fabric has a distinct pattern you can match the pattern with diagonal seam and probably will never know it.
You might have to buy a little more. Check the repeat and see if you can do this. If fabric has no distinct pattern then don't have to worry about matching. Is that 52 1/2 inch one one cut or two cuts or multiple cuts for border
Do you have a picture of the quilt.
Guess I am asking what you do next with the long strip
Then you might be able to use the larger piece as part of the backing