Worcestershire spinner Saeed Ajmal was Hampshire's tormentor on day three of their top-of-the-table LV County Championship Division Two clash at New Road.
Ajmal took seven wickets in an awe-inspiring display of off-spin bowling as Hampshire were made to follow-on after being bowled out for 219 in response to the Pears' first innings effort of 402 for nine declared.
The 36-year-old then struck just before stumps to leave Hampshire on 31 for one at the close - trailing by 152 runs - and Dale Benkenstein's side need to avoid defeat on Wednesday to ensure Worcestershire do not leapfrog them at the top of the Division Two standings.
Having finished Monday's play on 10 for one after Michael Carberry was dismissed by Jack Shantry with the first ball of the innings, Hampshire made steady progress, with Jimmy Adams and Will Smith charged with the task of getting their side close to, or even past, Worcestershire's commanding first-innings total.
Smith was particularly in good touch and plundered successive fours in the 30th over to bring up his fifty.
All seemed rosy for Hampshire in the final few overs before lunch but they were dealt a double blow shortly before the interval when Ajmal pinned Adams (40) leg-before-wicket in the 35th over before bowling Smith (67) through the gate four overs later to reduce the away side to 114 for three.
If Ajmal had been impressive in the morning, he was even better in the afternoon.
He put an end to Glenn Maxwell's innings, dismissing him lbw for 24 just as the Australian threatened to get into his groove, before bowling Sean Ervine (nought) in the same over, and then accounting for Michael Bates (nought), Matt Coles (19) and Danny Briggs (one).
Charles Morris and Joe Leach chipped in with the wickets of David Balcombe (nought) and James Vince (48) respectively as Hampshire failed to amass the runs needed to avoid the follow-on.
The heavens opened shortly after the end of the innings, giving Hampshire a chance to regroup after a morale-crushing day.
Play resumed shortly before 6pm after a 90-minute delay, with Carberry and Adams attempting to see out the 14 remaining overs scheduled to be bowled.
They almost did it, but Ajmal claimed his eighth wicket of the day by pinning Adams (nine) in front in the penultimate over to leave Hampshire with a mountain to climb if they are to avoid slipping to their first county championship defeat of the season.