The Chicago Cubs have been expected for weeks leading up to the trade deadline to get aggressive in making upgrades as they try to capitalize on their World Series window.

It’s no secret that by far their biggest need is starting pitching, and if they are going to have a chance to make a deep run this October, another arm is needed.

Chicago has been linked to just about every single available — and unavailable starter, and while time is running out, a deal still feels inevitable.

More News: Cubs Reportedly ‘Very Interested’ in Acquiring Rising Ace MacKenzie Gore

In his Sunday notebook, baseball insider Bob Nightengale of USA Today shed some light on just how desperate the Cubs are to trade for a starter by revealing who they would be willing to include in a deal for Pittsburgh Pirates star Mitch Keller.

“The Cubs desperately want another starter at the deadline, targeting Mitch Keller of the Pirates, and would include outfield prospect Owen Caissie to make it work,” Nightengale wrote.

The allure of trading for someone like Keller works in two ways.

More News: Cubs Considering Putting Together Trade Package for Atlanta Braves Star

For one, he has a 3.53 ERA and 1.160 WHIP with just 30 walks in 125 innings this season, pitching as steady as anyone in the National League right now.

The real attraction though — and the reason to be willing to give up serious assets — is the contract.

Keller is under team control for three more years after 2025 for roughly $16 million, $18 million and $20 million.

The market for starting pitching this past offseason was dramatically inflated, and having a reliable arm locked up for $20 million or less over three years is supremely valuable.

As for Caissie, it’s a tough sell to give up the potential future superstar.

More News: Cubs Could Use Their Top-Ranked Prospect To Land Difference-Making Pitcher

Chicago has had to watch former highly-rated prospect Cam Smith become an instant superstar as a rookie for the Houston Astros after sending him away in the Kyle Tucker trade.

Caissie has that same potential, playing the best baseball of his minor league career over the last couple of months.

In 81 games this year, the 23-year-old is slashing .278/.377/.563 with 20 home runs and 46 RBI for Triple-A Iowa.

The reality is that Caissie is big league ready right now, there just is simply not a spot for him.

Trading him is going to be very difficult, but if the Cubs get to deadline day and have yet to acquire a starter, they are likely going to be desperate enough to do just that.

For more Cubs news, head over to Cubs On SI.