Scott Kessler still can't find the value in Twitter.
The red-hot social media stock has shot up 40 percent since Dec. 11, making it one of the best-performing newly public stocks this year and granting it a larger market capitalization than most of the S&P index. But it all comes down to value and earnings for Kessler, an analyst at S&P Capital IQ.
Kessler has held a "sell" rating on Twitter since November and reiterated his recommendation Friday morning. His call contributed to a sharp 11 percent decline in the stock as of late Friday afternoon. (What are Twitter shares doing now? Click here)
"At the end of the day, we have thought and we continue to think the valuation is just initially stretched," Kessler said on "Squawk on the Street." "It's excessive. It appears now that we've approached some kind of mania. When that happens, you just kind of have to wait and see what happens."
(Read more: Chart of the Day: Bigger winner, TWTR or bitcoin?)