Sources: Pirates following Carlos Pena

MILWAUKEE -- Scouts from the Pittsburgh Pirates have been following Chicago Cubs first baseman Carlos Pena for more than a month, according to multiple major league sources.

The Pirates, currently involved in a four-team race to win the NL Central, are looking to add a big bat before baseball's July 31 trade deadline. At least one Pittsburgh scout will be on hand when the Cubs take on the Brewers on Wednesday night.

From the Cubs' perspective, Pena has picked a bad time to go into a slump. He is 0-for-15 in his past four games and has only three home runs in his past 22 games.

Pena is working with a one-year contract that makes him a free agent after the season. His current contract pays him $10 million over the next three years. He was paid $3 million after signing with the Cubs in early December. Pena will make $4 million during the 2011 season then gets the finally $3 million owed to him in January 2012.

Due to the fact that the Cubs have no prospects ready to play first base at the big league level, they may approach Pena about extending his stay in Chicago after the season ends.

Pena is batting .219 with 20 home runs and 50 RBIs on the season. Beyond those numbers, he has played Gold Glove defense for the Cubs and has taken on a leadership role with the team.

Pena told ESPNChicago.com on Sunday that he'd love to return to the Cubs next season.

Bruce Levine covers the Cubs for ESPNChicago.com