Option volume was unusually heavy on MGM Resorts International (NYSE:MGM - 12.95) yesterday, with roughly 20,000 calls and 21,000 puts changing hands on the casino stock -- representing 1.55 times MGM's average daily activity. The most active option was the weekly 1/11 13-strike call, where 4,829 contracts were traded.

The majority of these weekly calls traded at the ask price, suggesting they were purchased, and open interest jumped overnight by 2,295 contracts. As a result, it seems safe to assume new bullish bets were initiated at this strike on Tuesday.

By buying to open the weekly 13 call, traders are expecting MGM to rally higher through Friday's close. Based on the option's volume-weighted average price (VWAP) of $0.18, most of these speculators need MGM to rise above breakeven at $13.18 (strike price plus VWAP) in order to turn a profit. The shares settled yesterday at $12.95, so short-term bulls are banking on a gain of more than 1.8% over the next three sessions.

Call buyers are likely trying to capitalize on MGM's recent burst of positive momentum, with the stock having surged 11.3% already in 2013. The gaming issue is poised to continue its uptrend in today's trading, up 1.9% in pre-market action after the Macau government granted its seal of approval for a new Cotai casino.