Both players suffered major leg injuries last season.
Mitchell missed the entire year with a torn ACL. He had three sacks in 2006 and one in 2007 but was in line for an increase in playing time last season after Kenechi Udeze was diagnosed with leukemia.
But Mitchell was injured in the first preseason game and spent the entire season on injured reserve.
Mitchell says his rehab is going well and he hopes to participate in several minicamps before training camp begins at the end of July.
Gordon, who was showing promise as a nickelback and return man, had a gruesome lef ankle injury on a punt return against Green Bay in November.
Evans was a regular on the defensive line. He started the final two games of the regular season and the playoff loss to Philadelphia in place of the injured Pat Williams.
Retaining Evans would also help the Vikings should Williams lose his court battle with the NFL over a positive test for a banned diuretic. If Williams does not win the case, he will be suspended for the first four games of next season.
Tahi beat out Thomas Tapeh for the starting fullback job early in the regular season.