The teenager has been struggling for form and fitness since winning the US Open last autumn, so her 6-3 6-3 defeat to in-form, bold-hitting French world No.55 Caroline Garcia was not really a surprise on Wednesday.
It was, though, a huge let-down for a predominantly British audience who desperately wanted to see Raducanu go deep into what is only her second Wimbledon.
Garcia was always in command in the first set and gained a crucial edge midway through the second.
Unfazed by the atmosphere she sealed victory with a cross-court backhand at the first attempt.
At just 19, there will be plenty more Wimbledons for Raducanu, but for now, it is back to the gym and the practice court as she builds up to her title defence in New York.
Former champion Garbine Muguruza maintained her poor record of not reaching the second week at Wimbledon since winning in 2017 when she lost 6-4 6-0 to Belgian Greet Minnen.
The ninth-seeded Spaniard looked to have a game suited for Wimbledon when she followed up an appearance in the final in 2015 by defeating Venus Williams two years later, but it hasn't worked out like that.
On No.2 court, she made 33 unforced errors and hit only nine winners as she succumbed.
Also out is Anett Kontaveit, the low-profile second seed, hammered 6-4 6-0 by the power-hitting Wimbledon debutant Jule Niemeier.
The Estonian, who's reached No.3 in the world without ever having got past the quarter-finals of a grand slam, couldn't cope with Niemeier's booming groundstrokes and looked increasingly dispirited as she succumbed to the little-known German 22-year-old in less than an hour.
Karolina Pliskova, Jessica Pegula and Jelena Ostapenko, seeded six, eight and 12 respectively, all progressed.
Pliskova, last year's beaten finalist, defeated fellow Czech Tereza Martincova 7-6 (7-1) 7-5.
American Pegula, a quarter-finalist in Melbourne and Paris this year, beat Donna Vekic 6-3 7-6 (7-2) to reach the third round here for the first time.
Former French champ Ostapenko, semi-finalist at Wimbledon in 2018, despatched Yanina Wickmayer 6-2 6-2.
There were also victories for seeds Shuai Zhang and Sorana Cirstea.
Lesia Tsurenko won an emotional all-Ukrainian tie defeating No.29 seed Anhelina Kalinina.
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