Jim Edmonds, who spent eight seasons with the Cardinals before he was dealt last offseason, hit a pair of solo homers for the Cubs, connecting in the second and seventh innings off Braden Looper.
With the score 2-2, Derrek Lee drew a leadoff walk against Ryan Franklin (4-5) in the 11th and, running on a 3-2 pitch, took third on Aramis Ramirez's single to right center. Kosuke Fukudome was intentionally walked to load the bases.
Blanco, who entered in the 10th. lined a pitch over shortstop Cesar Izturis.
Bob Howry (5-4) pitched the 11th for the win.
Edmonds' stellar afternoon came on the Cardinals' first visit to Wrigley Field this season.
During Edmonds' return trip to St. Louis last month, Cardinals manager Tony La Russa was miffed about Edmonds' comments that he was happy to be with the Cubs and tired of talking about his past. Edmonds responded by saying La Russa ducked him before the first game of that series.
Edmonds appeared to enjoy his first homer Friday, pausing at the plate momentarily to watch it take off before rounding the bases. Before the drive, Edmonds was 0-for-7 this season against his former team.
His second homer, his 15th of the season, was an opposite-field shot to left-center. He ran quickly around the bases after tying the game but did come out of the dugout for a curtain call.
Joe Mather homered for the Cardinals, who had two runners cut down at the plate
- one on a squeeze bunt attempt in the fifth and the second when left fielder Alfonso Soriano made a great throw after catching a fly ball for an inning-ending double play in the sixth.