Chicago's lineup was made up mostly of regulars from last season, when the Blackhawks had 104 points and reached the Western Conference finals. The Capitals' lineup included mostly younger players and prospects.
Washington left wing Alex Ovechkin, the NHL's goal-scoring leader last season with 56, was a healthy scratch for the second straight game.
Sharp opened the scoring 4:52 in on a rebound of Dustin Byfuglien's shot. Skille gave Chicago a 2-0 lead at 5:54 of the second on a rising, screened shot from right wing.
Clark cut it to 2-1 midway through the second, when his centering pass intended for Wilson deflected in off the skate of Chicago defenseman Brent Seabrook.
A Blackhawks' preseason record 19,734 fans a sellout attended the game in the newly reconfigured United Center.
Chicago center Dave Bolland remains out with a lower-back injury. ... Washington right wings Eric Fehr and Tomas Fleischmann have undisclosed injuries. All three were regulars for their teams last season.
Copyright by STATS LLC and The Associated Press
Arena: United Center Location: Chicago, Illinois
Attendance: 19,734 (100.1% full)
Patrick Sharp Assist: Dustin Byfuglien, Duncan Keith
Jack Skille Assist: Duncan Keith, Ben Eager
Chris Clark Assist: Tom Poti, Kyle Wilson
Kyle Wilson Assist: Chris Clark
Mathieu Perreault Assist: Brendan Morrison, Oskar Osala