Worcestershire 271 and 147 for 6 (Libby 49, Neser 3-34) lead Glamorgan 139 (Byrom 57, Leach 6-44) by 279 runs
Joe Leach marked his return to first team action with career best figures of 6 for 44 to help Worcestershire establish control on day two of the LV=Insurance County Championship match with Glamorgan at New Road.
The allrounder has been side-lined since suffering a back problem in mid-May but quickly made his presence felt on a wicket of pace and bounce continuing to offer encouragement to the seamers.
His three-wicket burst on Sunday evening had put Worcestershire in the ascendancy and he continued in the same vein today to earn his side a lead of 132. Only opener Ed Byrom, with a fighting half century, offered much resistance.
Azhar Ali and Jake Libby then built on Worcestershire's position of strength with a second wicket stand of 87. But Michael Neser bowled an inspired late spell which brought him three wickets as the home side closed with a lead of 279.
Leach has been a talismanic figure for Worcestershire with the ball for many seasons since making the switch from initially being primarily a middle-order batter. The 31-year-old has that ability to take wickets in clusters which shows no sign of diminishing as he lifted his first-class tally past the 380 mark.
Byrom was making only his second Championship appearance in a season where he initially had minor surgery and then suffered a hip flexor strain. But he hit a career best 176 on his return to four-day action against Sussex at Cardiff earlier in the month and showed more defiance here against a probing attack.
Tom Fell came into the Worcestershire side for his first senior appearance of the season as a concussion replacement for Taylor Cornall, who was struck on the helmet by a delivery from Neser during Worcestershire's first innings.
Fell had last played at first-team level in the Championship match with Kent at Canterbury last September.
Leach struck in his first over of the day when beating the defensive prod of Sam Northeast, who was bowled. It became two wickets in two balls when Kiran Carlson pushed forward and was snapped up by Josh Baker low to his right at third slip
Charlie Morris was rewarded for a challenging opening spell when Billy Root was caught behind.
Leach returned to the attack shortly before lunch to have Glamorgan keeper Tom Cullen taken at first slip for his sixth scalp.
Michael Neser offered no stroke to Ed Barnard and was bowled before opener Byrom completed an excellent half century off 112 balls with eight fours. The innings was wrapped up when No. 10 Andrew Salter, who had opened in the first six Championship games, nicked Barnard to second slip.
Byrom was last out on 57 when he drilled Dillon Pennington to long-on.
When Worcestershire batted again, Ed Pollock's poor run continued when he drove at a widish delivery in Michael Hogan's opening over and was caught at first slip.
Azhar did the bulk of the scoring during the early stages of the partnership with Libby who gradually opened out. He cover-drove and on-drove Hogan for boundaries in the same over. But the Australian broke the partnership in his next over when Azhar on 42 was caught behind off a delivery which kept low.
Libby moved to within one run of his half-century before he tried to work James Harris to leg and was lbw. Fell was then undone by a lifter from Neser which he edged to give Cullen his seventh catch of the match so far.
Neser had more success when club captain, Brett D'Oliveira, was taken by Northeast low at second slip. First innings century-maker Barnard could only manage a single before he was bowled by Neser.