Surrey are without a host of players, including Jason Roy and the Curran brothers — Sam and Tom — at the IPL, as well as bowlers Rikki Clarke, Liam Plunkett (who is not injured) and Kemar Roach, who is in isolation after arriving in the UK.
Topley, whose fitness has prevented him playing much red-ball cricket in recent years, joined last summer and performed well in T20s. He has since signed an all-format deal and is joined in the seam attack by Jamie Overton.
Surrey boast five Test players in their top order, while Jamie Smith is set to fill the final batting spot.
Middlesex face Somerset at Lord’s, and must weigh up how to balance their five-man seam attack. Tim Murtagh, Toby Roland-Jones, Steven Finn, Tom Helm, Ethan Bamber and Blake Cullen are all in their 14-man squad, competing for four places in the XI.
Stevie Eskinazi captains in the absence of Peter Handscomb, while Thilan Walallawita is injured.