Anne Keothavong lost 6-2 6-3 to Daniela Hantuchova in the first round of the Aegon International in Eastbourne.
The British number one was broken four times as she struggled against the number eight seed.
reached the tournament proper after beating Bojana Jovanovski 6-3 6-2 in the final qualifying round.
In the men's event,
made it through to the second round with a 6-1 6-4 win over American Donald Young.
Jade Windley, ranked 501 in the world, did not make the main women's draw, losing 6-2 6-0 to Hungarian Greta Arn.
Arn will now play British number three
in the first round proper on Wednesday.
Robson was due to meet another Briton
in the third round of qualifying
but the Scot withdrew
with a neck injury.
Instead she made light work of world number 103 Jovanovski, winning in 71 minutes to advance to the main draw.
The 18-year-old, who has been handed a wildcard for Wimbledon, was never broken throughout the match and won 22 of 28 points on her first serve.
Keothavong, 28, will now hope British number two Baltacha is fit enough to take her place alongside her in the doubles.
In the men's draw Baker, ranked a career high 200 in the world, will now face either Germany's Philipp Kohlschreiber or Go Soeda of Japan, who meet on Wednesday.
"That's my best win in terms of ranking, no doubt about that," said Baker after his victory over 50th-ranked Young.
"My next goal is to get to 150. If I can, ranked 200, beat a guy who's in the top 50, there's no reason why I can't, a step at a time, [reach the top 50]."
The news was not so good for
who was beaten 4-6 6-1 6-4 by Australian Marinko Matosevic.
enjoyed more success, following her singles win over Jovanovski, by reaching the second round of the ladies doubles with
The British duo beat Anastasia Pavlyuchenkova and Lucie Safarova 6-2 6-3.
There was also success in the men's doubles as
combined to beat Mariusz Fyrstenberg and Marcin Matkowski 6-2 6-4.