Timmy and Percy

Those wearing Let Tim Smoke! T-shirts sold outside the SF Giants' stadium may have had the right idea. Two-time, defending Cy Young award winner Tim Lincecum is in a terrible slump, just after signing a $23-million dollar contract on the heels of a marijuana bust in the off season.
Attorney Tony Serra (the True Believer) propounds an interesting theory in Leah Garchik's SF Chronicle gossip column:

It's obvious...what has happened to impair his pitching brilliance. His decline occurred after his marijuana conviction in Oregon [actually, Washington]. He obviously has not 'medicated' since then. Baseball pitchers, like trial lawyers, have a 'high stress' vocation. Marijuana ably moderates stress. Lincecum suffers from 'cannabis deprivation'.

The pitcher, who may just be throwing his arm out of the action, at least has fared better than Vikings wide receiver Percy Harvin, who was hospitalized for severe migraine headaches after league policy disallowed his medical marijuana use for the ailment. Returning to practice, he had to be hospitalized a second time. Cindy Boren of the Washington Post describes what happened:

Harvin, who has battled migraines since he was 10 and sought treatment last year at the Mayo Clinic, had not practiced for two weeks because of migraines, returning to the field only Monday [August 16]. Suffering another attack Thursday, he managed to return to the field and looked up to the sky to field a punt. He doubled over, vomited and seemed momentarily unresponsive and was taken to the hospital. The scene was so disturbing for players that the rest of practice was called off.

According to Mike Meno of the Marijuana Policy Project,

during last year's NFL combine, Harvin, a promising prospect, tested positive for marijuana, and was subsequently drafted much lower than expected. The Vikings finally picked him 22nd overall, reportedly after a long talk about his marijuana use, and specifically, how it needed to stop if he wanted to keep playing.

Kareem Abdul-Jabbar, the top NBA scorer of all time, has admitted he uses marijuana for migraines. So many sports figures are found to be using marijuana (most recently, Miami Heat forward Udonis Haslem) that one wonders whether Serra is on to something.
Acknowledging to Sports Illustrated that as many as one third of potential draft picks have tried marijuana, the NFL is no longer disqualifying players who test positive for pot, but rather is evaluating them on a case-by-case basis. "If you knocked everyone off your [draft] board who has experimented with weed, you'd lose about 20 percent of your board, not to mention disqualify a few recent presidents," one NFL head coach said.
Dr. Frank Lucido, a medical marijuana specialist practicing in Berkeley, told the Wall Street Journal that two former NFL players with chronic orthopedic pain are his patients. "I say marijuana should not be a banned substance [in the NFL]. It has too many medical benefits," Lucido stated.
Ditto the NBA, MLB and the USA.
Ellen Komp edits the award-winning Very Important Potheads blog.