CHICAGO -- Cubs catcher Willson Contreras will be activated from the injured list and in the starting lineup on Tuesday, manager Joe Maddon said.

Contreras, 27, has been out a month with a hamstring injury that occurred as the catcher was running to first base in a game against the Milwaukee Brewers on Aug. 3.

He played three games at Triple-A Iowa in a rehab stint, going 1-for-7.

Contreras has had a rebound season, compiling a .890 OPS as a fixture in the middle of the Cubs lineup. He'll be behind the plate when Jon Lester takes on the Seattle Mariners on Tuesday night.

Maddon, speaking on the team's flagship radio station, WSCR, also indicated that Ben Zobrist would lead off in his first game action since May 6. Zobrist returned to the team over the weekend after taking a leave of absence stemming from marital issues.

Shortstop Javier Baez remains out of the lineup after jamming his left thumb on a slide on Sunday.

The Cubs began the day three games behind the St. Louis Cardinals in the NL Central.