Coach Giles White admitted morale in the Hampshire ranks was low after Somerset batted themselves into a strong position at Taunton.
The hosts started day three of this County Championship division one clash on 257 for five and looked pushed to challenge the visitors’ first-innings total of 338.
But despite a delayed start because of rain, Somerset closed the day on 534 for seven to ensure a last-day survival mission.
With the homside opening up a 196-run lead on a pitch still offering turn and occasional bounce, White said: ‘The dressing room is pretty low.
‘Our spinners didn’t bowl well and we were never able to put the batsmen under sufficient pressure.
‘Credit to Somerset for the way they played and applied pressure on our bowlers. They never allowed them to settle.
‘But we have to be pretty disappointed that the game has changed so much in a day.
‘We have not played to the level of our last couple of matches and now we will need to bat very well tomorrow.’
Jim Allenby (57) added 19 runs to his overnight score before he was caught behind by Lewis McManus off the bowling of Ryan McLaren with the new ball.
Lewis Gregory (61) followed suit after he edged a drip to slip off leg-spinner Lewis Crane.
But that was it for Hampshire, with unbeaten duo Roelof van der Merwe (91) and Craig Overton (97) sharing an eighth-wicket stand of 132 to give the visitors plenty of work to do.