Those calls lock in the price investors must pay for the stock. If it rallies in coming weeks, they will earn big leveraged gains. The February calls bought earlier in the month, for instance, tripled in less than two weeks. If Credit Suisse pushes lower, however, losses will pile up quickly.
Options require much less capital than owning the stock. More than 10,000 contracts traded in the June 31s, the equivalent of about 1 million shares at a fraction of the cost.
The European bank's shares ended the session up 0.38 percent at $26.71.
More than 16,000 options traded in the name overall yesterday versus a daily average around 2,900. Almost 14,000 of those were calls, a reflection of the session strongly bullish sentiment.
—Najarian has no positions in CS.
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Pete Najarian is a professional investor, CNBC contributor, regular co-host of CNBC's "Fast Money" and co-founder of OptionMonster.com.