The team also signed offensive lineman Vinston Painter to the active roster, added cornerback Tye Smith to the practice squad and released linebacker Amarlo Herrera from the practice squad.
Hall was lost to a season-ending torn ACL suffered against the New York Giants on Sunday, while Lichtensteiger has a calf strain. With Shawn Lauvao also dealing with a moderate ankle sprain and cornerback Bashaud Breeland straining tendons in his right ankle, the Redskins moved to improve depth along the offensive line and in the secondary.
Spencer Long is the backup center and left guard, and Washington didn't have another center on the roster. Sullivan, 31, started for seven seasons for the Minnesota Vikings before sitting out last season following a pair of back surgeries, and lost a training camp battle for the center job to Joe Berger.
Long was also the backup left guard after battling Lauvao for that position throughout training camp. That means second-year pro Arie Kouandjio could take over at left guard. He appeared in just three games last season and has been inactive the first three weeks of 2016.
There is another option. Left tackle Trent Williams slid inside to left guard against New York, and Ty Nsekhe replaced him at left tackle. General manager Scot McCloughan praised Nsekhe over the summer as a player who could start for half of the 32 NFL teams.
The decision: Is Washington better with Nsekhe at tackle protecting quarterback Kirk Cousins' blind side and Williams adjusting inside? Or is it a total waste to move a four-time Pro Bowl left tackle away from his natural position when Kouandjio could simply slide in at left guard?
"That's something that we've got to look at. (Williams is) so good at tackle," coach Jay Gruden said Monday. "But he actually played pretty darn good at guard. He's a great athlete. He'd probably be a good center, too. We'll just have to evaluate that situation and see how it goes. See how Arie does at left guard. Ty is an excellent player, there's no question about it. But to move your Pro Bowl left tackle out of the mix to guard is something that is a little unique and hard to do."
Hall was hurt late in the second quarter of a 29-27 win over the Giants while tackling wide receiver Odell Beckham Jr. He also collided with cornerback Dashaun Phillips on the play and immediately reached for his right knee.
Washington's starting free safety this season, Hall missed just 11 games in his first 10 NFL seasons. He became a defensive captain, a vocal locker room presence whose absence in the room was palpable when he tore his Achilles tendon in 2014
Now, at age 31, Hall will have to decide if he has more football left in him, although he indicated on Twitter on Monday that he plans to return. A typical ACL recovery process is six to eight months. He could be ready for the start of training camp next July.
"We'll have to see," Gruden said. "I think he's got to really take a look at it and see where he is once he does the rehab if he wants to try it again."
Phillips, who spent all offseason and training camp holding off third-round draft pick Kendall Fuller for the slot cornerback position, has a hamstring injury and might not play this weekend. Fuller played better at the end of the preseason, but the former Virginia Tech star has yet to be active for a game.
Phillips struggled at times against a strong contingent of slot receivers for the Pittsburgh Steelers, the Dallas Cowboys and the Giants. However, Gruden conceded Phillips' injury could leave the door open for Fuller to make his NFL debut against the Browns.
"The thing with Phillips -- we don't know if he's gonna be available this week or not," Gruden said. "With Fuller sitting here, he is obviously our No. 1 option A. And we're excited to see him play."