James Ward will take his Queen's Club campaign into Friday after bad light stopped play with the British number two level at one set all against defending champion Sam Querrey.
The Londoner, 24, had taken the second set to make it 3-6 6-3 in the third-round match when play was called off for the day at 2044 BST.
Ward enjoyed the best win of his career in beating fourth seed Stanislas Wawrinka in round two, and remains in sight of another shock victory as American Querrey struggles with an elbow problem.
The Briton held his own until the eighth game and looked in charge of that at 40-0, but the errors crept in and Querrey took five points in succession to break before serving out the set moments later.
It was a sharp dip in fortunes for Ward, and when a mishit Querrey return became a winning drop shot at the start of the second set, he found himself under pressure again.
A break point duly arrived for the American but Ward's nerve held and he fired down a big serve to stop the rot, before roaring with delight when he moved ahead at 4-2 with some brilliant returning.
The 6ft 6in Querrey, who had twice required treatment on his elbow, was struggling to find his usual pace on serve and Ward took advantage by closing out the set, albeit after a dramatic final game in which he saved a break-back point.
With the light fading, but far from gone, there was a decision to be made about whether to play a final set, and Querrey's reluctance appeared to be the key as the umpire confirmed that was it for the night.