Sales of his number 17 jersey are robust and the social media aggregation website Topsy says that over the past seven days, “Lin” has been mentioned more than 140K. He even got a shout-out on Twitter from Phoenix Suns’ point guard and two-time NBA MVP Steve Nash.

On Feb. 4, Lin played his first starring role for the New York Knicks as the point guard racked up 25 points in 95-92 win over the New Jersey Nets. Lin-mania kept building as the undrafted Harvard graduate outplayed Kobe Bryant in a 95-82 victory over the Los Angeles Lakers on Friday, and then on Saturday Lin helped lead his NBA team to a 100-98 squeaker over the Minnesota Timberwolves, the team’s fifth-straight win.

Although Bryant says he “doesn’t even know what Lin has done,” shareholders in Madison Square Garden, Inc., the parent company of the Knicks, do: Since February 4th MSG’s stock price has increased from $29.32 to $3.15, or 6 percent, adding $139 million to the company’s market value. During the same period the S&P 500 has gone up less than 1 percent.

How much is the Jeremy Lin brand worth, assuming he assisted in the stock’s appreciation and remains the real deal? Numerous factors impact MSG’s stock price, of course. But aside from Lin most of the news surrounding MSG in recent weeks has been negative, including its battle with Time Warner and its recent earnings release which showed profits falling 22 percent in the second quarter compared with the prior year.

The Knicks had $226 million of revenue during the 2010-11 season, roughly equating to 20 percent of MSG’s overall revenue. Obviously, you cannot assign Lin one-fifth ($28 million) of MSG’s $139 million increase in market value since he began his magical run (in the past we have determined athlete brand values are the amount by which their endorsement income exceeds the average of the top peers in their sport, but that methodology can’t be applied to Lin, who was a no-name player until very recently).

But we can still get a reasonable estimate. The New York Times reports that Lin has helped push up television ratings for the Knicks 66 percent over last season. So if we give Lin credit for half of the $28 million, his brand weighs in at $14 million, which would place him tied with Bryant for sixth among the top athlete brands in the world.

I expect Lin’s endorsements to reach that mark in the near future if he can keep up his stellar play on the hardwood.