The two centre-halves who will probably start this weekend’s Old Firm derby for Rangers have one goal between them this season, Philippe Clement couldn’t think of a better time for them to add to their accounts. The Gers boss has spoken recently about his love of set-pieces but there is something clear amiss when two such dominant headers of the ball don’t seem to be getting on the end of crosses. One former Rangers star who has been a matchwinner in the past is Filip Helander with his 2021 header the last time Philippe Clement’s side won a meaningful league derby. Rangers set-piece woes could…