Sadler, who also won the $100,000 Nationwide Dash 4 Cash bonus for the victory, had battled a flu bug for the previous three days, at one point spending 36 hours in bed. But when he arrived at the track Saturday, he felt the worst was behind him and was ready to practice and then race on Sunday.
"I'm still not 100 percent, but it feels good to win here in Chicago," Sadler said. "My wife and I came here with another couple, which also happens to be my doctor, and we had to put him to work.
"We drank a lot of fluids and I had to have a few IVs just to stay hydrated."
Give third-place finisher Justin Allgaier a big assist to Sadler's win, as he blocked runner-up Ricky Stenhouse Jr. several times in the green-white-checkered finish that turned the scheduled 200-lap event into a 201-lap finish.
"We were trying to get to Elliott and working both the high and low line," said Allgaier, who won this race last season. "At the end, we just couldn't hold off Ricky, but I'm very proud of this Brandt Chevy team and what we were able to do today."
Stenhouse eventually got past coming out of Turn 2 in the final lap, but didn't have enough in his car to pass Sadler. Stenhouse had dominated much of the race, including winning the pole earlier Sunday.
The final battle to the finish line was set up when, with seven laps remaining, Sam Hornish Jr. tapped the rear of Kyle Busch's car, sending it careening into Brendan Gaughan and putting both vehicles into the wall, bringing out the caution. While it was a tough break for both Gaughan and Busch, the incident was the best thing to happen for Stenhouse, as it set up a two-lap drag race to the checkered flag.
"I feel real bad about it," Hornish said. "I looked down because it looked like one of our hood pins was coming loose, then I looked up and got right into the back of Kyle's car. I get along real well with Kyle and, while he had already gotten on his plane and flown out, I apologized to (team manager) Rick Ren and also apologized to Brendan."
Busch finished 27th while Gaughan wound up right behind in 28th.
Stenhouse's bid for the victory was hurt when Brad Sweet spun for the second time in the race with 33 laps remaining, Stenhouse was caught on pit lane as the caution flag fell, dropping him from first to 10th when the race returned to green flag conditions.
Sadler assumed the lead at that point and never yielded in the remainder of the event.
"We were in the right place at the right time," Sadler said. "Ricky had the strongest car all day, but we kept working at it and eventually got into the right position.
"It was a big win, we won the Dash 4 Cash ($100,000 bonus), we kept our lead in the points and we go now to Indianapolis next week for the first-ever Nationwide Series race at Indianapolis Motor Speedway."
Still, Stenhouse got a great jump on the restart, rode around the track on the high line and began his quest to regain the lead, passing six cars and gaining three spots in the following two laps. He halved Sadler's two-second lead to just one in seven laps and the pole-sitter appeared as if he would finish off what he started, but it was not to be.
Allgaier made a bid on the second-to-last lap to overtake Sadler, but didn't have a strong enough car. While he held off Stenhouse as long as he could, Allgaier eventually yielded to the pole-sitter.
Stenhouse wound up leading 135 of the 201 laps, while Sadler led 35.
Allgaier finished third, followed by an outstanding run by series veteran Kenny Wallace and Michael Annett.
Rounding out the top 10 were Austin Dillon, Parker Kligerman, Hornish, Cole Whitt and Ryan Truex.
Danica Patrick finished 14th, the last car on the lead lap.
The points standings stayed the same, with Sadler remaining atop the Nationwide hill. He leads Austin Dillon by 11 points, followed by Stenhouse (19 points back), Hornish (minus-42) and Allgaier (minus-78).
1. (15) Elliott Sadler, Chevrolet, 201, $88,468.
2. (1) Ricky Stenhouse Jr., Ford, 201, $75,593.
3. (16) Justin Allgaier, Chevrolet, 201, $43,468.
4. (11) Kenny Wallace, Toyota, 201, $26,950.
5. (14) Michael Annett, Ford, 201, $31,043.
6. (2) Austin Dillon, Chevrolet, 201, $30,343.
7. (5) Parker Kligerman, Dodge, 201, $27,203.
8. (3) Sam Hornish Jr., Dodge, 201, $26,713.
9. (8) Cole Whitt, Chevrolet, 201, $24,618.
10. (9) Ryan Truex, Toyota, 201, $24,943.
11. (6) Brian Scott, Toyota, 201, $23,368.
12. (7) Mike Bliss, Toyota, 201, $23,018.
13. (22) Joe Nemechek, Toyota, 201, $22,293.
14. (13) Danica Patrick, Chevrolet, 201, $21,768.
15. (18) James Buescher, Chevrolet, 200, $22,093.
16. (24) Mike Wallace, Chevrolet, 200, $21,893.
17. (32) Travis Pastrana, Toyota, 200, $23,768.
18. (25) Timmy Hill, Ford, 200, $21,043.
19. (21) Brad Sweet, Chevrolet, 200, $20,918.
20. (28) Josh Richards, Ford, 199, $15,000.
21. (12) Johanna Long, Chevrolet, 199, $20,668.
22. (27) Jeremy Clements, Chevrolet, 199, $20,518.
23. (17) Jason Bowles, Toyota, 198, $20,368.
24. (19) Eric McClure, Toyota, 198, $20,243.
25. (30) Tayler Malsam, Toyota, 197, $20,578.
26. (35) Tanner Berryhill, Toyota, 194, $13,500.
27. (4) Kyle Busch, Toyota, Accident, 193, $14,100.
28. (10) Brendan Gaughan, Chevrolet, Accident, 192, $19,643.
29. (20) Jamie Dick, Chevrolet, 192, $13,050.
30. (26) Erik Darnell, Chevrolet, 179, $19,668.
31. (36) Benny Gordon, Chevrolet, Transmission, 60, $12,770.
32. (33) Danny Efland, Chevrolet, Engine, 47, $12,635.
33. (37) Tim Schendel, Chevrolet, Engine, 28, $12,525.
34. (41) Morgan Shepherd, Chevrolet, Handling, 19, $12,415.
35. (40) Matt Carter, Chevrolet, Handling, 18, $12,310.
36. (29) Blake Koch, Chevrolet, Ignition, 14, $12,275.
37. (39) Tim Andrews, Ford, Rear Gear, 13, $12,240.
38. (38) TJ Bell, Chevrolet, Vibration, 13, $12,186.
39. (42) Mike Harmon, Chevrolet, Overheating, 12, $12,070.
40. (34) Chase Miller, Chevrolet, Vibration, 11, $12,030.
41. (31) Stephen Leicht, Chevrolet, Clutch, 6, $11,965.
42. (43) Carl Long, Chevrolet, Overheating, 4, $11,935.
43. (23) Jeff Green, Toyota, Vibration, 4, $11,887.