Jackson had 126 yards on four catches in Washington's win over Philadelphia on Saturday.
"We feel confident in what we did," Kelly said, according to Calvin Watkins of ESPNDallas.com. "He played real well against us. Give him credit."
Jackson had career-highs in receptions and receiving yards in 2013, his first season under Kelly. The Eagles released him in March, reportedly due to concerns about his off-field behavior.
Jackson had 243 receiving yards in two games against the Eagles this season. He has six games with at least 115 yards.
Philadelphia's loss Saturday eliminated the Eagles from playoff contention. They conclude the regular season on Sunday against the New York Giants.
- Dan Gartland