MLB.com's Bill Ladson reported Tuesday that Capps, who was not tendered arbitration by the Pirates, planned on making a decision by Wednesday.
Grabow signed a two-year contract on Nov. 20 with the Cubs and gave Capps a little inside information.
"I basically told him about the organization and how the guys are in the clubhouse," Grabow said Tuesday from his Arizona home. "If he comes to the Cubs, he's coming to a contender."
The Cubs' starting pitchers go deep in games, which, Grabow said, could mean a lot of meaningful innings for Capps. The difference could come down to what Capps wants to do. The Nationals are looking for a closer, while the Cubs already have named Carlos Marmol their closer. Marmol took over in mid August for Kevin Gregg and went 11-for-11 in save situations. Marmol also walked a lot of batters.
Grabow said Capps is exactly what a manager wants -- he's durable and throws strikes.
"I told him, if you come to the Cubs, you might not close right away, but things happen," Grabow said. "[Capps] is a great guy. He'll take the ball every single day. He's a bulldog. He's the sort of guy you want in your bullpen."
Grabow wasn't too concerned about Capps' 5.80 ERA this past season with the Pirates.
"I think he's going to bounce back this year," the lefty said.
The Cubs' offseason wish list includes a veteran right-handed reliever to set up Marmol. The rest of the bullpen will be young, with Angel Guzman, Justin Berg, Esamilin Caridad, John Gaub, Sean Marshall, Jeff Samardzija, Tom Gorzelanny, David Patton, Jeff Gray and Rule 5 pickup Mike Parisi among the candidates. Marshall, Samardzija and Gorzelanny will also vie with Carlos Silva for the fifth-starter spot.