They look like they were processed seperately which makes it look weird to me.
It might be the fact that used a cut out of a colored layer of the same photograph.
Since there is white in the stitching my eye easily points out that the white on the denim is not desaturated and not part of the same group of whites that belong in your desaturated image.
not a big fan of selective colouring either. Why did you choose the waistcoat to be the coloured item in this particular piece? Is there a reason you want to draw the viewers eye there?