The 2013 offseason has been relatively busy for the Chicago Cubs.

Despite the fact that the Cubs are still in a rebuilding phase, they went out and signed starting pitchers Scott Baker (h/t ESPN Chicago) and Edwin Jackson (h/t ESPN Chicago).

Scott Baker will be looking to bounce back in Chicago after missing some of 2011 and all of 2012 with an injury.

Edwin Jackson was brought in to help round out Chicago’s rotation and eat up some innings for the next four years.

Now, general manager Jed Hoyer would be smart to go out and sign Shaun Marcum.

But why?

They’ve already signed two starting pitchers this offseason and Marcum probably won’t help carry them to the postseason this year.

He would, however, provide another stable arm to help improve Chicago’s starting rotation.

Marcum has posted an ERA of 3.70 or lower in each of his past four seasons (spanning from 2008-2012, as Marcum did not play in 2009).

His WHIP has been below 1.20 in three of those four years, and his record comes in at 42-26 over that span.

The 31-year-old would also add another veteran presence to the Chicago Cubs, and could remain an effective pitcher for the next several years—especially if the Cubs are able to compete by 2015 or 2016.

With his statistics, Marcum would also jump Edwin Jackson (whose ERA and WHIP have both been higher than Marcum‘s) for the second spot on the Cubs’ depth chart.

If Chicago thinks it’s wise to bolster their rotation this offseason, signing Shaun Marcum would be just as good of a move as the signings of Baker or Jackson as it seemingly shows no downside whatsoever.

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