This article is part of our Rising Star Portfolios series.

I've already made one purchase of Madison Square Garden (Nasdaq: MSG) shares. Now I'm back for another chunk.

Why? The Knicks landed Carmelo Anthony, after weeks of high drama that would make a telenovela look tame. 'Melo inked a three-year, $65 million extension with the New York basketball team, which Madison Square Garden conveniently owns. The move makes the company more attractive, so I'm adding shares to my Special Situation portfolio.

Having superstar players can be especially valuable for Madison Square Garden, which was spun off a year ago from parent Cablevision (NYSE: CVC). Anthony's debut for the Knicks saw the MSG network – owned by the same parent – score its highest rating for a regular-season Knicks game in 16 years, quadrupling this year's average viewership. Such high ratings indicate that the superstar can make Madison Square Garden's media network more valuable, even if ratings are not at record levels every game night. Still, the Miami Heat, which scored LeBron James in the offseason, has seen a doubling of local ratings so far this season.

In addition, Anthony's presence increases the value of the team, which was already rated by Forbes as the most valuable NBA franchise, worth $655 million. In contrast, LeBron James's departure from the Cleveland Cavaliers last year sunk the value of that team by 26%, according to Forbes.

If Carmelo can help lead the Knicks deep into the playoffs, he could really provide another revenue driver to a stock that already has several, as I detail in my original buy decision. So with the arrival of 'Melo and the undervalued nature of the stock, I'm doubling down on shares of Madison Square Garden, adding another 3%, or $500, to my Special Situations portfolio.

Interested in other media stocks? Here's one that I call free money.

This article is part of our Rising Star Portfolios series, where we give some of our most promising stock analysts cold, hard cash to manage on the Fool's behalf. We'd like you to track our performance and benefit from these real-money, real-time free stock picks. See all of our Rising Star analysts (and their portfolios) here.

Jim Royal, Ph.D., does not own shares in any company mentioned here. The Fool owns shares of Madison Square Garden. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.