Sloppy cricket from Sri Lanka allowed the West Indies to build on a 96-run first-innings lead, with the home side extending their overall advantage to 165 at lunch on the fourth day of the second and final Test in Antigua on Thursday.
After Kemar Roach polished off the Sri Lankan first innings by taking the last two wickets in the space of three deliveries in the fourth over of the morning, West Indies went in pursuit of quick runs to consolidate their position and reached 69 for two.
They lost John Campbell early, the left-handed opener again dismissed to a catch by wicketkeeper Niroshan Dickwella off seamer Suranga Lakmal.
New batsman Jermaine Blackwood lived a charmed life immediately on his arrival at the crease, surviving a confident leg-before appeal to Lakmal and then being badly dropped at first slip by Lahiru Thirimanne off the other opening bowler, Vishwa Fernando.
His luck eventually ran out with his score of 18, Dushmantha Chameera, the third pacer in the Sri Lankan bowling attack, inducing an edge for Dickwella to take his seventh catch of the innings.
Blackwood has promoted up the batting order as regular number three Nkrumah Bonner continues to be hampered by whiplash-like symptoms sustained while fielding on the second day of the match.
West Indies captain Brathwaite, who should have been run out in a mix-up with Blackwood, only to be reprieved by Sri Lankan counterpart Dimuth Karunaratne's failure to collect a return to the bowler's end, will resume in the afternoon session on 22 alongside Kyle Mayers (nine not out).
Sri Lanka's efforts to limit West Indies' progress have been hampered by what appears to be a serious leg injury to Lasith Embuldenya, the left-arm spinner being taken off the field on a stretcher when an attempted sliding save in the outfield went badly wrong.
Their day had started badly when Pathum Nissanka could only add two more runs to his overnight 49 before top-edging an attempted pull-off Roach for substitute fielder Hayden Walsh Jr to take his second catch of the innings at deep square-leg.
Roach then wrapped up the innings by having last man Fernando caught behind to finish with the best figures of three for 58.