From the bull's perspective, GrubHub had a lot going for it. The company talked about how its total addressable market could be as large as 350,000 restaurants, which is 61 percent of all restaurants in the United States.
At the same time, it was the only nationwide platform out there; serving 30,000 restaurants and the numbers have only become larger since its IPO. It also wasn't hostage to advertising in order to make its money.
But since April of 2015, the stock has plunged to $24 from $47. In other words, it has almost been cut in half in a matter of months.
What went wrong?
While GrubHub is still expanding rapidly, the growth has dramatically slowed. In its latest quarter, GrubHub delivered 36 percent revenue growth, down from its 75 percent growth rate the year before.
This deceleration gave Cramer the impression that its rising competitors, such as Postmates and Uber Eats, could be taking a toll on GrubHub's business.
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But worst of all, GrubHub's daily average orders—a very important key metric—increased by just 22.5 percent, down from 33 percent at the end of 2015. GrubHub claimed there were weather and service outages, but in Cramer's opinion there is clearly a trend here that shows GrubHub is slowing.
GrubHub did propose a plan to reinvigorate its business, and management indicated it would spend $10 to $20 million to move beyond online ordering and into delivery. But Wall Street was not impressed, as the spending suggested that the economics of the delivery space are not very attractive.
At the end of the day, there is nothing worse for a company's earnings than competition. GrubHub may have not had much competition when it came public 18 months ago, but now there is a lot more competition and it is evident in its decelerating growth rate.
"Maybe GrubHub can turn things around, but I suggest you wait and see if the growth here can stabilize, because at the moment this former high flier has now entered the danger zone, making it too risky for me," Cramer said.