While Leeds celebrated a famous victory after ending - against the odds - Bath's imperious unbeaten English cup final record, Tykes skipper Balshaw saw his Lions hopes suffer a potentially damaging blow.
Balshaw will undergo a scan on Monday to gauge the extent of a thigh muscle injury that forced him off after just four minutes at Twickenham.
Initial fears are that the England full-back might have suffered a muscle tear, which could put his Lions tour prospects in grave danger ahead of departure to New Zealand on May 25.
"I pulled up at the end of training on Wednesday with a strain in my quad muscle, but it felt okay in the warm-up," Balshaw said.
"When I had a first run and tried to kick on a bit, I just felt a bit of a pop. I've got to wait now, until I have a scan on Monday.
"Obviously, there is a bit of worry there, but I can't really say much on the matter until Monday. I wasn't 100 per cent really, but I desperately wanted to play against Bath.
"Unfortunately, I lasted less than five minutes.
"It's one of these things, when you feel a pull and it could be a little strain or it could be a big tear. You don't really know until you have seen the doctors," Balshaw added.
"I've been involved in matches before when I have been less than 100 per cent, and I have come through them."