The Ricketts family acquired a majority interest in the Cubs in 2009, ending the Tribune years. Apparently handcuffed by the Tribune's bankruptcy and the sale of the club to the Ricketts family, the Cubs' quest for a NL Central 3-peat started with notice that there would be less invested into contracts than in previous years. Chicago engaged St. Louis in a see-saw battle for first place into August 2009, but the Cardinals played to a torrid 20–6 pace that month, designating their rivals to battle in the Wild Card race, from which they were eliminated in the season's final week. The Cubs were plagued by injuries in 2009, and were only able to field their Opening Day starting lineup three times the entire season. Third baseman Aramis Ramírez injured his throwing shoulder in an early May game against the Milwaukee Brewers, sidelining him until early July and forcing journeyman players like Mike Fontenot and Aaron Miles into more prominent roles. Additionally, key players like Derrek Lee (who still managed to hit .306 with 35 HR and 111 RBI that season), Alfonso Soriano and Geovany Soto also nursed nagging injuries. The Cubs posted a winning record (83–78) for the third consecutive season, the first time the club had done so since 1972, and a new era of ownership under the Ricketts' family was approved by MLB owners in early October.

Answer this question, if possible (if impossible, reply "unanswerable"): Who did Chicago engage in a see-saw battle for first place into August 2009?
St. Louis