Sheehan: Bullpen upgrades a must for first-place Cubs

The Cubs were one of the teams that kicked off the midseason trade market, reacquiring Chris Coghlan from the A’s last week for Arismendy Alcantara. The trade helped the Cubs patch some short-term roster issues with a player with whom they’re familiar, but the deal wasn’t just about June. The Cubs, who ended the weekend with the best record in baseball and a 12 1/2-game lead over the Cardinals, are already thinking about their postseason roster.

Coghlan has played all four corners plus second base, and after wandering in the wilderness for a few years since winning the 2009 NL Rookie of the Year Award, has hit .246/.326/.419 from 2014 through today. He’s a tactical weapon with a broad skill…