With three of the eight places still to be filled, other Britons could join Baker in the men's draw, but it is more likely that players such as Alex Bogdanovic, who is ranked above the Glaswegian, will have to enter the qualifying tournament. Four British women have been named, among them Laura Robson. Scotland's Elena Baltacha qualifies by right.
Baker, who went down 6-1, 6-4 to his opponent from Uzbekistan on Centre Court, will now be able to play at Eastbourne next week in search of more grasscourt experience. After losing to Istomin he admitted that he had found it difficult to bridge the gap between this status of match and the level of tournaments he has been playing in lately.
"It's tough stepping up to the level of the player I was playing today from the usual matches," the British No 3 said. "I've been playing against people probably from 150 to 300ish, so it's a step up.
"I think I said yesterday that it would be a question of how quickly I can adapt to the level, because playing on a court like that, as enjoyable as it is – the court itself is bigger. It's a different perception."
Baker is currently ranked just outside the top 250 in the world, whereas Istomin is 72nd and has been as high as No 57. The difference in status was especially marked in the first set, which was over in 22 minutes, and the second threatened to go the same way after the Scot lost his serve in the opening game. He dug in, however, fighting back to hold serve in the fifth and seventh games when his Moscow-based opponent looked like breaking him again. An easier hold saw Baker stay in the contest at 4-5, but Istomin's own serve was impregnable, and the match was over after only 68 minutes.
Men: Jamie Baker (GB); Teimuraz Gabashvili (Georgia); Nicolas Kiefer (Germany); Andrey Kuznetsov (Russia); Kei Nishikori (Japan); Three places still to be filled.
Women (all GB): Katie O'Brien; Laura Robson; Melanie South; Heather Watson; Four places still to be filled.