While present at pre-season testing and race weekends, the tyre test will be his first opportunity to get behind the wheel himself.
“After the Grand Prix weekend, Mick will also get his first real-world taste of the W14 on the second day of the Pirelli tyre test,” confirmed team boss Toto Wolff.
“He has done a great job with the team so far, working hard back in the simulator and giving valuable input trackside.
“We're looking forward to him getting his first taste of on-track running this year, and sure it will help him in his role as reserve driver.”
Tyre testing has long been used as a way to bank seat time for drivers.
Teams are limited in what they're able to do to and with their cars as Pirelli defines the run programme for each.
As a result, the outings offer little value beyond building familiarity and comfort in a current-spec car, making it an ideal opportunity for reserve and third drivers.
Despite the risks associated with running the package around the confines of Monaco, the decision was taken to introduce it there regardless.
Mercedes expects to get a better understanding of the revisions this weekend given the uniqueness of the Monte Carlo streets offered comparatively little insight.
“Spain will provide an opportunity for us to establish a new baseline with the W14,” Wolff said.
“It is a track that we are familiar with, although the removal of the final chicane will make it a much quicker lap.
“It comprises a wide range of corner types; that provides a good opportunity for us to learn about the new package.
“We don't expect to see a step change in performance, but we're hopeful it will provide a more stable platform.”
Opening practice for the Spanish Grand Prix begins at 13:30 local time on Friday (21:30 AEST).