Worcestershire 159 for 2 (Ali 60*, Haynes 42*) lead Leicestershire 148 (Barnard 3-45) by 11 runs
The Running Foxes were dismissed for 148 in 52.2 overs with Worcestershire’s loan signing, Matthew Waite, picking up two wickets.
They struggled to deal with a disciplined attack who had secured maximum bowling points by the 42nd over.
Waite has joined Worcestershire on a short-term loan move from Yorkshire as a replacement for Joe Leach, who has a back injury.
Waite has not played for Yorkshire since featuring in the Vitality Blast quarter-final against Sussex at the Emirates Riverside last August.
Parkinson won the toss and elected to bat but his side were soon on the back foot against the probing Worcestershire attack.
Leicestershire would have been reasonably content to lose only one wicket in the first hour – Hassan Azad lbw to Pennington – on a slowish wicket with some up and down bounce.
Rishi Patel was undone by a delivery from Morris which stopped on him and popped up a catch to short mid wicket.
His dismissal brought Ackermann to the crease in need of runs after only 24 in the previous six innings, including a pair against Middlesex. But his poor run of form continued as he made only a single before nicking Barnard to first slip.
Lewis Hill went leg before to a Morris delivery swinging into him and Wiaan Mulder departed after a brilliant catch by Josh Baker at third slip off Barnard.
Rehan Ahmed became the 500th player to play first-class cricket for Leicestershire but it was not a day he will remember fondly. He went to pull Pennington and top edged to Pollock at first slip without troubling the scorers.
Ben Mike and Harry Swindells decided attack was the best form of defence before Waite was rewarded with two wickets in two overs.
Swindells got in a tangle and ballooned the ball onto the offside where Jack Haynes, running across from second slip, took the catch and Mike (16) played down the wrong line and was bowled.
When Ed Barnes chopped on to Josh Baker, Leicestershire were still two runs shy of a hundred but resistance came from the last-wicket pair of Parkinson (22) and Chris Wright (27 not out) who added 50.
Barnard claimed his third scalp when Parkinson presented Pollock with his third catch of the innings.
Pollock was in typically aggressive form with a series of boundaries when Worcestershire launched their reply.
Jake Libby, a century-maker against Derbyshire, also looked in good nick as the pair put on 48 in 9.3 overs.
Mulder checked their progress when trapping Libby lbw for 17 and he followed it up with the wicket of Pollock (32), who picked out Ed Barnes at deep backward square leg.
But Azhar and Haynes featured in a century partnership for the third successive match. The duo had shared in stands of 195 versus Durham and 187 against Derbyshire.
Azhar produced some delightful drives and cut shots and brought up his half-century from 71 balls with six fours. Haynes also continued the form which had brought centuries in the previous two games.