My only concern: Would either player be a good fit with the Redskins?
The short answer: No.
I'll get to Incognito's play in a minute, but I'll start with the obvious angle about why you wouldn't want him. He's just not the sort of guy you'd want in your locker room. Say what you want about the Redskins' offensive line, but in general it's a pretty cohesive group on and off the field. Guard Chris Chester likes talking politics and the others will chime in as well. I don't see them wanting to be around a guy like Incognito.
Also, the Dolphins reportedly considered cutting him last offseason, despite him making a Pro Bowl. He was not a good fit in their zone blocking scheme and is best described as a mauler in a man-blocking scheme. The Redskins will continue to run a zone blocking system under new coach Jay Gruden.
Then there's this comment from former coach Rick Venturi, who was on St. Louis' staff when Incognito played there -- as was Redskins defensive coordinator Jim Haslett. Venturi told ESPN.com of Incognito: "He's a runaway train. When we had him, and I think actually for a while in terms of his actual on-the-field stuff, I actually think he improved in Miami. But for us, he was selfish, he was loud, tried to intimidate. It was just his style. I say selfish, from the standpoint that he was highly penalized. He cost us games, cost us yardage. I was never a fan of his."
By the way, when I used to do some part-time work for the Sporting News, one of my tasks was a midseason survey of four or five players. Every year, Incognito was the runaway winner of players I spoke to as the NFL's most dirtiest.
As for Martin, he's an excellent fit in a zone scheme because of his footwork, which is why Miami drafted him 42nd overall in 2012. But he was a two-time All American in college who was not highly thought of by all. Pro Football Weekly, for example, wrote that Martin was an "overhyped developmental project who needs to get stronger." Here's a list of what others said.
That assessment looked accurate during Martin's time playing in Miami, whether he was on the right or left side. He did not distinguish himself at all. Perhaps he'd be better off at, say, right guard. But strength will be an issue no matter what spot he plays.
Had Martin come to Washington in the first place, which wasn't going to happen obviously, then perhaps he would have avoided certain issues now so well exposed. But he would not have avoided speculation about whether he could play. The Redskins could use more help along the line. The last thing they need is a player who needs a lot of work to develop -- they already have guys like that -- not to mention the circus atmosphere that his presence would create for a first-time head coach.