Worcestershire's 2017 overseas player John Hastings picked up three wickets on his Specsavers County Championship debut against Glamorgan at the SWALEC Stadium.
The home side were bowled out for 207 in just 40.4 overs as Worcestershire claimed maximum bowling points.
Glamorgan initially struck back with the ball either side of a 79 run partnership between Tom Fell and Joe Clarke.
But Tom Kohler-Cadmore and Ben Cox batted superbly and brought up their 100 partnership in 19 overs before bad light and rain halted play 12.3 overs.
Kohler-Cadmore ended the day unbeaten on 52 and Cox, in a new elevated number six slot, was 41 not out as Worcestershire closed on 180-4.
New skipper Joe Leach exercised the right to bowl first on a cloudy morning and he and new ball partner Hastings soon had the home side on the back foot.
Hastings made the first breakthrough in the fourth over with 14 on the board as Clarke held onto a low catch at third slip to account for Jacques Rudolph (2).
Then Leach struck twice in two balls to reduce the home side to 28-3.
First Nick Selman (16) edged through to keeper Cox and the next delivery accounted for Colin Ingram who was squared up as Hastings showed a safe pair of hands at fourth slip.
Hastings enjoyed another success as Aneurin Donald was bowled for three and then Chris Cooke (5) was run out by Tom Fell's direct throw from mid wicket.
Glamorgan were then 46-5 in the 13th over.
David Lloyd went for an aggressive approach, hitting Hastings over the square leg boundary and pulling Josh Tongue for six.
Tongue, on his Championship debut, had replaced Hastings after an initial spell of 6-2-14-2 and Leach made way for Jack Shantry after an opening burst of 8-2-37-2.
The wickets continued to tumble with Brett D'Oliveira pulling off a superb diving catch at point after Kiran Carlson (13) cut away at Ed Barnard.
It became 82-7 when Harry Podmore (1) edged Shantry and keeper Cox pulled off an excellent catch diving to his right.
Lloyd struck a third six, this time off Barnard, as he continued his aggressive approach.
But Barnard bowled Marchant de Lange (11) with what proved to be the final ball before lunch with Glamorgan 105-8 off 27.2 overs
Lloyd remained undefeated on 44 and after the interval he and Lukas Carey (39) adopted an ultra aggressive approach.
They added 68 in quickfire fashion before Carey was bowled by Hastings with a delivery which hit the top of the off stump to leave Glamorgan on 173-9.
Lloyd's fine knock ended on 88 when he was caught at cover by Hastings off Shantry. He struck three sixes and 10 fours in his 103 ball knock.
Hastings finished with 3-57 from 11 overs, Leach 2-60 from 11 overs, Barnard 2-32 from six overs and Shantry 2-12 from 5.4 overs.
Worcestershire ran into early trouble when they started their reply with openers Daryl Mitchell and D'Oliveira both dismissed for nought.
Mitchell gloved a Carey delivery through to keeper Cooke and then D'Oliveira nicked a rising ball from Michael Hogan to the keeper.
Fell and Clarke lifted the total to 80 and played some fine shots but both departed at that total.
Clarke, having made 39 from 57 balls with six fours, gave Cooke a third catch, down the legside off Lloyd.
Then Fell, who struck five fours in his 35 off 62 balls, played back to Carey and was bowled.
Kohler-Cadmore and Cox wrestled the initiative back to Worcestershire as they raced along at more than five runs an over.
Kohler-Cadmore went to his half century off 74 balls with nine balls and Cox again showed his worth on a day which ended for Worcestershire as well as it had started.
Worcestershire Director Of Cricket, Steve Rhodes, said: "We bowled and fielded well in the morning, but then Glamorgan did well to pass 200 in difficult conditions.
"After losing our two openers for one run, all credit to the middle order, who have put us in a good position.”
Glamorgan's top scorer David Lloyd said: ”Lukas Carey and Michael Hogan did very well to get us the batting point, and we were in a good position with them at 1-2.,
"But after the rain break we seemed to lose our way a little, and we must get early wickets in the morning."