There are actually damn few truly defining moments in life, in sports, or in politics. Certainly interesting stuff happens all the time and a lot of it is important, but "defining"? To quote the venerable John Wayne, "Not hardly." Though even I have to admit that sometimes the cow-dropping media hype we are hosed down with 24 hours a day does occasionally get it right: "Pirates of the Caribbean III" was indeed an important commentary on the history of world culture.But today there is a classic pro-sports defining moment scheduled for 5:00PM Pacific Standard Time. It's Game Four of the 2012 National League Championship Series between the San Francisco Giants and the St. Louis Cardinals. Currently the Cards led the best of seven series 2 games to 1.Why "defining"? Because two-time Cy Young Award winning pitcher Tim Lincecum is on the mound for San Francisco. The same Tim Lincecum who put up the following numbers in the Giants' 2010 World Championship postseason: 4-1, with a 0.92 WHIP, and 43 SOs in 37 IP. And the same Tim Lincecum who posted a 23-29 win-loss record in 2011-12, topped off with a nasty 5.18 ERA in 2012.Tonight Lincecum is the starting pitcher Giants Manager Bruce Bochy has chosen to stop the bleeding before the Cardinals take an intolerable 3-1 lead in the NLCS. It's a very big gamble for the Giants and a classic defining moment in Lincecum's career. After so many bad months and false starts the past two years, can Lincecum get it done with everything on the line and the national media watching and analyzing every second?All the past awards and stellar numbers, the positive attitude, and having supportive teammates won't be nearly enough. This is the MLB postseason and it's strictly about hits, walks, and earned runs. Tim Lincecum has an inner competitive beast that is being held in check by apparent flaws in his mechanics and the loss of about 5 MPH on his fastball. Which he has to somehow overcome tonight.