How long will the Chicago Cubs’ pitching success last?

Sep 25, 2013; Chicago, IL, USA; Chicago Cubs starting pitcher

(49) delivers a pitch against the Pittsburgh Pirates during the first inning at Wrigley Field. Mandatory Credit: Rob Grabowski-USA TODAY Sports

With a dominant performance against the St. Louis Cardinals on Saturday afternoon at the Friendly Confines, Jake Arrieta became the latest member of the Chicago Cubs pitching staff to put together an impressive outing – joining the likes of staff ace Jeff Samardzija, right-hander Jason Hammel and 2013 National League All-Star Travis Wood.

Entering Sunday night’s series finale against Mike Matheny and the Cardinals, Chicago has tallied 15 quality starts so far this season, which comes out to 53.5 percent of the team’s games – which ranks near the middle of the pack among all 30 big league clubs, and ninth in the National League.

The staff’s earned run average of 3.76 ranks in the bottom half of the National League, but the performance of a spotty relief corps is largely to blame for that number being as high as it is. The five members of Chicago’s starting rotation currently hold earned run averages of 1.98, 2.08, 0.00, 3.35 and 5.24. Granted, Arrieta has just one start under his belt, but we’ll take it – for now.

Jackson is the lone sore spot in the rotation now that righty Carlos Villanueva (1-5, 9.95 ERA) has moved back to the bullpen to make room for Arrieta in the Cubs’ rotation, and simply put, he appears to be slated in that spot for the foreseeable future. Jackson is currently in the second year of a four-year, $52 million contract – one far too rich to simply have him work as a long relief man a couple of times each week.

Across the board, his numbers have been poor with Chicago; he has a 5.24 ERA (as opposed to a 4.49 ERA in his big league career), a 1.573 WHIP (alongside a 1.44 career mark) and simply put, just isn’t hitting his spots, as evidenced by his 1.53 SO/BB ratio – the worst in his 12 big league seasons, in which he has averaged 1.97 SO/BB.

What all Cubs fans need to understand is that Edwin Jackson will probably never be a sub-4.00 ERA pitcher in Chicago. He probably won’t ever win 15 games either – something only delusional fans would even anticipate, given he has never accomplished that fear in Major League Baseball. His best season came over a half decade ago, with the Tampa Bay Rays back in 2008, when he went 14-11 with a 4.42 ERA – a far cry from his performance in Chicago thus far.

That being said, if Jackson can simply get his earned run average back to the mid-4.00 range and he pitches around 175 innings, he can still be fairly valuable to the organization moving forward as a back-of-the-rotation starter. However, this becomes more problematic post-July when we could see both Hammel and Arrieta dealt, not to mention Samardzija.

A rotation without Hammel, Arrieta and Samardzija would be disastrous for the remainder of this season, regardless of what types of prospects and talent are netted in return. While the long-term benefits could continue to help shape the Cubs’ rebuilding effort, this team would be trotting out the likes of Chris Rusin and Carlos Villanueva when their respective rotation spots are slotted. And as much as Wood impressed last season, he’s certainly not an ace – at least not on a quality Major League pitching staff.

So, enjoy it Cubs fans. While this team’s starting pitching has been, for the most part, throughout the season’s first month, as the summer progresses and the prospective trade chips begin to fall, things could fall apart in a hurry on the North Side.