The hosts have seen off Edinburgh Accies, Ayr and Stirling County lately to leave them in fifth place in the table while wins against Boroughmuir, Hawick and Glasgow Hawks see Heriot’s in third place.
For this intriguing looking derby, Watsonians have Charlie McKill back from Scotland Sevens duty to start in the second-row while young winger Lomond MacPherson is given a starting spot.
Watsonians head coach Steve Lawrie said: “Having scraped past Stirling County a fortnight ago in a performance full of defensive resolve we have worked hard in training to develop a couple of areas that we believe are key to improving our overall output.”
Loosehead prop Josh Scott, second-row Adam Sinclair, centre Robert Kay and teenage winger Jack Blain return to the visitors’ starting XV with Martin Bouab and Andrew Simmers added to a strong-looking bench.
Heriot’s head coach Phil Smith said: “The fixtures leading up to Christmas are going to be extremely important in deciding where teams end up – starting against our oldest rivals under lights on an international weekend could not be bigger.”