Richard Oliver will make his LV= County Championship debut in Worcestershire's Division Two encounter versus Glamorgan at New Road from tomorrow.
Shropshire skipper Oliver, who recently signed a contract with the Pears until the end of next season, has been promoted to the first team following an outstanding innings of 292 not out for Worcestershire's second XI this week.
Director of cricket Steve Rhodes told the club's official website: "Anyone who makes a score like that in the second team, just about 300, deserves to get a chance in the first team, and that's what he is going to get.
"We are obviously looking forward to him hopefully carrying on that form but we've been very impressed with his run-scoring ability in league cricket, second-team cricket and hopefully now in first-team cricket.
"He is learning all the time about red-ball cricket. He has played a handful of second team matches with the red ball but he has already got a hundred and now a double-hundred.
"Hopefully he can not change anything and hopefully the occasion doesn't get the better of him but I don't think it will because he has already shown in T20 cricket that he can handle the crowds and the sort of pressure that comes with playing for the first team."
Oliver, a revelation in the Rapids' NatWest T20 Blast team, will line-up alongside Moeen Ali after the England batsman, fresh from scoring a maiden Test century, was given permission to play at New Road.
Batsman Matthew Pardoe and all-rounder Ross Whiteley have been omitted from Rhodes' 12-man squad.
Worcestershire are a point behind leaders Hampshire, who are currently playing third-placed Surrey at the Kia Oval.
Glamorgan, sitting in fourth position, are unbeaten in their last four championship outings.
Alex Gidman will continue to skipper Gloucestershire in the absence of injured Michael Klinger against Essex at the Essex County Ground.
The Australian opening batsman is occupying the sidelines with a broken toe.
New signing Adam Rouse, the matchwinner in the Blast victory over Kent Spitfires last night, replaces Patrick Grieshaber behind the stumps while Jack Taylor and David Payne are included in a 13-member squad.
Third-bottom Essex, who have all-rounder Graham Napier back but are without England skipper Alastair Cook, have not won a four-day game since beating Derbyshire in their opening match of the campaign.
LV= County Championship Division Two facts
* Six of the last seven championship fixtures between Essex and Gloucestershire have been drawn. Essex won the other match, at Chelmsford in 2012.
* Worcestershire are unbeaten in their last 11 championship matches, their longest unbeaten run since they went 16 games without defeat in 2002/03.
* The two bowlers with the lowest championship boundary percentages (minimum 200 balls) both play for Essex: Tom Westley (2.4%) and Greg Smith (3%).
* Seventeen of championship top wicket-taker Saeed Ajmal’s 44 scalps have been lbw, five more than any other bowler.
* Ben Wright has scored 75 per cent of his championship runs in boundaries, the highest proportion across both divisions (minimum 200 balls).