Mike Williams is listed as questionable.
McCoy appeared in just two games this season. He was injured two weeks ago against the Arizona Cardinals. After an interception, McCoy was in on the tackle when an offensive lineman fell into his left knee.
The former Southern California player was drafted in the sixth round in April.
Trufant took a knee to the head from New Orleans Saints running back Chris Ivory that knocked him out of the game a week ago. He passed an array of tests during the week ranging from physical stress tests to reciting numbers backward to clear him to return to practice Friday.
"He did everything just right as far as passing the tests, made it through fine today. So he'll be playing Sunday," coach Pete Carroll said of Trufant. "It's great to have [him] out there for us, you know with all his experience and all that."
Trufant stressed the importance of getting a day of work in before taking the field against the Chiefs.
"I think it was big for me to get out there and run around and just kind of feel the game," Trufant said. "You can watch film, you can do all that kind of stuff, but for me I'm a feel type of guy. I got to feel it and I've got to go through it."
Williams is a question mark. Carroll has been vague about the nature of Williams' foot injury throughout the week referring to it as an "unusual" injury and something the team's doctors hadn't seen before. However, when asked about what the injury is, he merely called it a "foot strain."
Williams still had a protective boot on his left foot and did not practice Friday. Carroll said he will work out before the game and be a game-time decision.
"We don't know," Carroll said. "We're going to work him out on game day. We're going to hold him out all the way until then. If he can go and go full-speed then he'll be in as well."
"As we look at it now we think that if he takes today and we [still]) got tomorrow, a whole another day, we have a better shot at it," he said.
Information from The Associated Press was used in this report.