The Patriots (6-1) had been given a two-game roster exemption by the NFL, allowing Mankins to practice without counting against the active roster after he reported to the team on Tuesday and signed his restricted free-agent tender.
The move means the Patriots have decided to forgo the exemption and activate Mankins in time to likely play and start Sunday's game against the Cleveland Browns (2-5).
A source told ESPN NFL Insider Adam Schefter that Mankins will start on Sunday against the Browns.
Without Wheatley, a third-year cornerback who had not played this season after suffering a preseason foot injury, the Patriots have Devin McCourty, Kyle Arrington, Jonathan Wilhite and Darius Butler on the roster at cornerback, as well as second-year Tony Carter on the practice squad.
Backup tackle Quinn Ojinnaka also has experience playing guard.
The Patriots also released inside linebacker Tyrone McKenzie, a 2009 third-round draft choice who spent the first eight weeks of the season on the Patriots' practice squad, on Saturday.
McKenzie had previously passed on the opportunity to join another team's 53-man roster, but was interested in seeking other opportunities within the NFL.
McKenzie, the 97th overall pick last year, got off to a tough start in New England when he tore his ACL in 2009 rookie mini camp. He missed his entire rookie season because of the injury. While he was expected to be part of the mix on 2010, rookies Spikes (second round) and Fletcher (free agent) leaped him on the depth chart.
Mike Rodak contributes to ESPNBoston.com's coverage of the Patriots.