After pounding out 17 hits and winning easily in the series opener, the Red Sox captured a tense struggle in Game 2, despite stranding a dozen runners.
Colorado will be at home for Game 3 Saturday night in the first World Series game ever played in Denver.
Okajima struck out four and did not allow a hit over 2 1/3 before being replaced by closer Jonathan Papelbon, who got the last four outs and moved the Red Sox within two wins of their second World Series title in three years.
Colorado scored in the first when Willy Taveras raced home from third on Todd Helton's ground out. Jason Veritek's sacrifice fly tied it in the fourth.
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