The 24-year-old fell ill while in the field on day one on Thursday and was replaced by substitute Josh Cobb, and head coach John Sadler admitted there is no guarantee Vasconcelos will be okay for the start of Friday's play at 11am.
“Ricardo was feeling fine in the morning, but then started to feel nauseous after going out on to the field," revealed Sadler.
"He was then sick in the dressing room when he came off. Hopefully he will be okay after he’s had a night’s sleep and some more rest.”
Northants will certainly be hoping their captain will be well enough to open the innings when that moment arises, with Surrey ending day one on 261 for six from 96 overs.
There was a century for England Test opener Rory Burns (107), while all-rounder Sam Curran, who was born in Northampton, added a free-flowing 71 not out.
For Northants, Luke Procter was the pick of the attack, taking three for 51 from 19 overs, while Ben Sanderson claimed two for 56 from 25.
It was a solid bowling performance, but Sadler felt the attack, without the rested Gareth Berg who was replaced in the starting line-up by left-arm spinner Simon Kerrigan, could have done started better.
“I think we are still right in the game," said the head coach.
"Perhaps we didn’t get it quite right in the first session, but Luke Procter’s three wickets were crucial for us in the first half of the day and he’s been superb for us with bat and ball."
Burns was delighted to get his season up and running with his century, having scored only 119 runs in his previous six innings, and he revealed he too would have bowled first if he had won the toss.
“It was a good day and hopefully we can go on again and put a decent total on the board," said the left-hander.
"I am very pleased to get the hundred and I’ve been tweaking things a little bit with my batting in pre-season and in the early season games so it’s nice to see it pay off.
“Northants put us in on that pitch for a reason, and I would have also opted for us to bowl first if I had won the toss. It has offered the bowlers something all day.
"Sam Curran’s innings has been very important for us and he’s been batting very well in these early games.”