Analysts' said Google's decision to replace Singhal with Giannandrea was a sign features dependent on machine learning, such as Google's personal assistant, which answers questions and conducts searches with the push of a button, will play a larger part in the future of search.
"The fact that they got the head of artificial intelligence to take over the role is very telling of where they expect to evolve going forward," said Sameet Sinha, a senior equity analyst at B. Riley & Co.
Google's stock fell after Singhal announced his retirement. While analysts were hesitant to cite his departure as the primary reason for the stock hit, several said it was a factor.
"Amit was very well respected and had been at Google from the start and helped to define search as we know it," said Sinha.
Recon Capital Partners Chief Investment Officer Kevin Kelly said "weakness in tech stocks that are trading at high valuations" as well as Singhal's departure were at play in the stock's decline.
Google closed down 4.03 per cent at US$749.38, the largest decline since August.