World Cup-winning captain Martin Johnson thinks England would miss prop Dan Cole more than anyone in their current side.
The Leicester Tigers tighthead has started every match in England's 16-Test winning streak, dating back to the 2015 Rugby World Cup.
Although the 29-year-old's performances rarely grab the headlines, Johnson believes he is an unsung hero in Eddie Jones' squad.
"Dan Cole at tighthead is a constant in the England team," Johnson told Sky Sports.
"He does not get a lot of mentions but that is good in a way. It is like referees -- you only mention them when they have bad games.
"England are pretty solid in the set-piece and I think they would miss him more than anyone -- he is potentially England's least replaceable player."
Meanwhile Johnson -- who played 84 Test for England at lock -- believes Maro Itoje is best suited to playing in the second row.
Last year's World Rugby Breakthrough Player of the Year has started the first two rounds of the Six Nations at blindside for England, with Chris Robshaw out injured.
"They [England] have got guys injured so they need to play him there. If he can do both then fantastic because it gives you options," Johnson said.
"If you want to go for a big No. 6 then you can stick him there, then put him in the second row for the last 20 minutes or so and bring a different type of player on.
"I would probably keep him in the second row though.
"Itoje is very athletic and strong and when you have him in the second row he is a very athletic and strong second rower.
"When you put him in the back-row, you are dealing with a lot of other athletic guys so my preference would be to keep him in the second row and to be the most athletic team you can be.
"I think if you have him and a Courtney Lawes and then a dynamic back-row then you have a dynamic back five."