FOXBORO, Mass. — Three unidentified defensive players joined the New England Patriots on the practice field Monday afternoon.

The players — who wore Nos. 46, 64 and 66 — warmed up with the linebackers, and Nos. 64 and 66 later split off to run through drills with the defensive ends.

In other news, running back Rex Burkhead and wide receiver Matthew Slater both returned to practice. Burkhead didn’t practice last week and sat out Friday’s preseason game against the Detroit Lions. Slater had been on the shelf for more than three weeks after suffering an injury early in training camp.

Rookie defensive end Deatrich Wise appeared to be a full participant at practice for the first time since suffering a head injury in New England’s preseason opener. Wise is one of just three healthy D-ends remaining on the Patriots’ roster after the team released Kony Ealy and Caleb Kidder over the weekend.

Wide receiver Malcolm Mitchell, safety Nate Ebner, tackles Nate Solder and Tony Garcia, and linebackers Shea McClellin and Harvey Langi all were absent from Monday’s session.

Mitchell, Garcia, McClellin and Solder all have been regulars on the injury report in recent weeks. Ebner and Langi, meanwhile, had not missed a practice before Monday. Solder has yet to play in the preseason but did practice last week.

A source told the Boston Herald’s Jeff Howe that Solder’s injury isn’t considered serious.

As expected, neither wide receiver Julian Edelman nor defensive end Derek Rivers attended practice. Both are recovering from torn ACLs and are expected to miss the entire regular season.

The Patriots close out their preseason schedule Thursday night against the New York Giants at Gillette Stadium.

UPDATE (2:24 p.m. ET): Solder told ESPN.com’s Mike Reiss he did, in fact, practice Monday but arrived after the open media portion had concluded.

The identities of the three mystery players also were revealed after practice.

No. 46 is Christian Kuntz, a linebacker out of Duquesne. No. 64 is former North Carolina defensive end Mikey Bart. No. 66 is Nick Usher, a linebacker out of UTEP. All three are undrafted rookies.

Thumbnail photo via Troy Taormina/USA TODAY Sports Images