The 28-year-old averages 53.11 in this season’s County Championship, including two centuries, and will take the place of Gary Ballance, who has been ruled out of the Kia Oval showdown with a broken finger.
Westley also notched an unbeaten hundred for the England Lions against a full-strength South African bowling attack at Worcester last month, which may have held some sway with England’s hierarchy.
Middlesex’s Dawid Malan, meanwhile, could also make his international red-ball debut in what will be the 100th Test to be played at the Kia Oval after he was named in England’s 13-man squad for the clash.
Left-hander Malan made his England bow in last month’s T20 fixture against South Africa in Cardiff and scored 78 as the hosts claimed a 19-run series-clinching victory.
The 29-year-old, who averages 42.50 in the championship this term, told City A.M. in April that he felt he had done enough to be considered for senior England selection and warranted an opportunity.
He said: “Other guys get picked who are younger and probably only had one good year, not three, four, five or six good seasons together. It does get a bit frustrating.”
Malan could be picked if England opt for an extra batsman following their 340-run annihilation at Trent Bridge earlier this week which left the four-match series locked at 1-1.
Despite enjoying a prolific summer with Surrey and fellow opener Keaton Jennings struggling at the top of England’s batting order, Mark Stoneman has once again been omitted from the squad.
Stoneman is the third-highest run-scorer in domestic cricket’s top-flight this season behind Surrey team-mate Kumar Sangakkara and Ballance. Uncapped seamer Toby Roland-Jones has retained his place in the squad.