Glamorgan threatened Worcestershire's dominance at times but the visitors were well placed at the end of the opening day in Cardiff. When rain and bad light ended play with 12.3 overs remaining, they had reached 180 for 4 - a deficit of only 27.
David Lloyd scored 88 and Glamorgan's last two wickets added 102, to rescue them from 105 for 8, and they then reduced Worcestershire to 1 for 2 at the start of their innings. But they recovered thanks to an unbroken partnership of 100 for the fifth wicket between Tom Kohler-Cadmore and Ben Cox.
Joe Leach, in his first game as Worcestershire's captain, opted to field first under cloudy skies, and his decision was soon vindicated as both Glamorgan openers were back in the pavilion after the opening overs. John Hastings, in his first game as Worcestershire's overseas player, took the first wicket with his eleventh delivery when Jacques Rudolph edged to slip, before Leach had Nick Selman caught behind.
Lloyd, who bagged a pair in the first game at Northampton last week, was off the mark with a six over fine leg, but then lost partners in quick succession, as Leach squared up Colin Ingram first ball, Hastings bowled Aneurin Donald, and Chris Cooke failed to beat Tom Fell's direct hit from midwicket to leave Glamorgan 46 for 5.
Wickets continued to fall after lunch, with Kiran Carlsen and Marchant de Lange falling to Ed Barnard and Harry Podmore removed by Jack Shantry. Lloyd and Lukas Carey retrieved Glamorgan's parlous position, however, with an attacking partnership of 68 at eight runs an over. Carey belied his position of No. 10 with an array of attractive strokes, and when he was out Glamorgan were within 27 runs of a batting point. This was achieved as Michael Hogan helped add a further 34, before Lloyd's splendid innings ended 12 runs short of his century, when he lofted Shantry to extra cover.
Carey then made immediate inroads when Worcestershire batted, when, after bowling a wide with his first ball, he had Daryl Mitchell caught by the wicketkeeper two deliveries later. In the next over Hogan dismissed Brett D'Oliveira in identical fashion, before Fell and Joe Clarke settled down to share a partnership of 79 for the third wicket. Clarke, who toured with the England Lions during the winter, played an assured innings before he was caught down the leg side off Lloyd and, with no addition to the score, Carey bowled Fell in the next over
With Worcestershire 80 for4, Glamorgan were back in contention, but Kohler-Cadmore and Cox consolidated their team's position with the best partnership of the day. They were rarely in trouble against Glamorgan's five-man pace attack, with Kohler-Cadmore striking Carey for three successive fours when the young seamer overpitched.
Kohler-Cadmore reached his fifty shortly before the close and, with Cox also showing impressive form, Glamorgan will need to take early wickets if they are to restrict Worcestershire to a modest first-innings lead.