No there isn't. He is no better than any guy anyone could put in there at the #5 spot. Take my pathetic team. at the five spot they can go Noesi, Montras, Beck, Drabek, Johnson, Penny, Carroll. Just from that batch they get the same or better from EJAX at less bucks.
The dodgers are starting Carlos Frias with a 4.54/4.25 ERA/FIP
The angels are starting Matt Shoemaker with a 4.80/4.51 ERA/FIP and Jared Weaver with 4.75/4.75
The Astros are starting Collin McHugh with a 4.35/3.87, Scott Feldman with a 4.93/4.38 ERA/FIP, and Roberto Hernandez with a 5.18/4.85
The yankees are starting CC Sabathia at 5.25/4.32, and Nathan Eovaldi at 4.50/3.53
The O's are starting Chris Tillman at 4.96/4.13, Kevin Gausman at 5.40/3.52, Miguel Gonzalez at 4.21/4.94
The Rays are starting Alex Colome at 4.70/4.56
The Blue Jays are starting Drew Hutchison at 5.19/3.75 and Dickey at 4.70/4.98
The Roays are starting Jeremy Guthrie at 5.36/4.70 and Danny Duffy at 4.24/4.40
I could literally go on and on here. Jackson has a 3.19/2.83 ERA/FIP this year. Now I'm not saying the cubs would get anything good for him(talking Barney level trade here) but there quite literally isn't enough starting pitching on the market for all these contending teams and if the guys listed above are starting what do you think their AAA looks like if someone were to get injured? What do you think Jackson will pass through waviers never to be heard from again? The cubs might not be able to trade him but I will guarantee some team picks him up if he hits FA after waviers.