Excitement and uncertainty surround the Chicago Cubs and St. Louis Cardinals as the teams prepare to open a three-game series Tuesday night.

The series opener in St. Louis features two longtime rivals tied for first place in the National League Central. It also marks the last game before Wednesday afternoon's trade deadline -- with both teams vowing they have enough to win now but also scouring the market for a boost.

St. Louis is coming off a road series in which it dropped two of three games against the Houston Astros. The Cubs also are looking to regroup after dropping two of three games on the road against the Milwaukee Brewers.

The teams have played each other nine times this season, and the home team has won every game. The Cubs swept a three-game series at Wrigley Field from May 3-5, the Cardinals swept a three-game series at Busch Stadium from May 31-June 2, and the Cubs answered back with a three-game sweep at Wrigley from June 7-9.

The Cardinals are 29-22 at home this season.

Meanwhile, the Cubs are 20-31 on the road, which is a far cry from their 36-18 record in Chicago.

Cardinals right-hander Adam Wainwright (7-7, 4.63 ERA) is scheduled to make his 20th start of the season. He picked up a win his last time out despite giving up four runs in five innings at the Pittsburgh Pirates.

In 48 career games (39 starts) against Chicago, the 37-year-old Wainwright is 16-12 with a 4.06 ERA. This will be his fourth start of the season against the Cubs, having posted a 1-2 record with a 4.67 ERA.

The Cubs will counter with right-hander Yu Darvish (3-4, 4.54), who is set to make his 22nd start. He has been sharp since the All-Star break, allowing four runs on 10 hits in 18 innings for a 2.00 ERA. He has walked two and struck out 21 during that time.

The 32-year-old Darvish is 0-0 with a 5.40 ERA in two career starts -- both this season -- against St. Louis.