The 29-year-old renowned fighter was troubled by a thigh strain and looked on the verge of being knocked out by Jodie Burrage on Wednesday when she served at 5-6 in the deciding set and fell 0-40 behind but she somehow turned it around to win 6-4 4-6 7-6 (7-3).
There was further disappointment for British fans in the following match at a packed Devonshire Park when Emma Raducanu was beaten 4-6 6-1 7-6 (7-4) by 19-year-old Australian Maya Joint.
Second seed Krejcikova, who beat Italy's Jasmine Paolini to win last year's Wimbledon title, seemed in control when leading by a set and a break of serve but needed treatment on her leg.
Burrage, ranked 164th in the world, played impressively to hit back though and broke Krejcikova's serve to level the match -- one point being awarded to her after a forehand from her opponent found its way through a hole in the net.
The 26-year-old British player kept just ahead in the decider but she could not take any of the three match points that came her way and then a costly double-fault in the tiebreak offered up match points to Krejcikova, who made no mistake.
Krejcikova, who also saved match points on Tuesday against home player Harriet Dart, has won two singles matches in a row for the first time in an injury-hit 2025.
"Another tough match," Krejcikova, who also has a French Open singles crown to her name, said on court.
"Brits know how to play on grass and it's hard to play against them but happy I'm through.
"I was going through a difficult moment at the beginning of this year but I'm happy I'm here and can keep finding the level that I know I can reach."
Krejcikova will next face French qualifier Varvara Gracheva.
