Neither Alphabet Inc.'s (GOOG  ) (GOOGL  ) co-founder Sergey Brin, nor current CEO Sundar Pichai have directly admitted it, but a former Google engineer warned that the threat from AI was "near inevitable" more than five years ago.

What Happened: Google's fumbles with its Gemini AI chatbot and the subsequent admittance of the mistake by Brin have reinforced concerns that the search giant is feeling threatened by AI chatbots, which include Perplexity AI and OpenAI's ChatGPT.

Earlier, Brin said Gemini's image generation was messed up, and the company did not test it adequately before rolling out the feature to the public. While that shows a lack of quality control at the search giant, it also points to a much larger issue.

However, a former Google engineer sounded the alarm about the threat posed by AI to the company's primary revenue driver.

According to internal emails revealed during the ongoing Google antitrust lawsuit, Eric Lehman rang the caution bells at the company. In fact, he sounded almost certain about his gut feeling and was ready to bet on it.

"None of us can see the future, but my bet is that this is nearly certain to be true within 5 years and could be true even within 6 months."

"My guess is that the advantages of our current approach will eventually crumble," Lehman explained, adding that machine learning technology was far outpacing traditional methods.

"I'm inclined to think that this future is near-inevitable."

What Happened: Google Search revenue for the fourth-quarter 2023 stood at $48.02 billion, accounting for nearly 56% of the company's total revenue during the quarter. Given that it accounts for half of the company's top line, it is vital for its financial health.

While Brin thinks the Gemini issue is "messed up," Pichai called it "completely unacceptable."

Whether Google fixes Gemini in time or not remains to be seen.