Joe Launchbury injured his elbow in England's 18-11 win against Italy and Geoff Parling suffered a stinger in his shoulder - but both locks came through a lineout session at 8.30am on Thursday to seal their places in the team.
Owen Farrell has also recovered from injury to reclaim the fly-half jersey as one of four changes Lancaster has made for the RBS 6 Nations title decider.
Tom Croft will start at blindside flanker in only his seventh appearance since returning to action after recovering from a broken neck that almost left him paralysed.
Croft has replaced James Haskell, Joe Marler has reclaimed the loosehead prop position from Mako Vunipola and England will start with Ben Youngs at scrum-half alongside Farrell.
Farrell missed the game against Italy with a thigh strain but he was passed fit on Monday and returns to the side in place of Toby Flood, with Youngs replacing Danny Care at scrum-half.
"I am delighted Owen is fit - he is a big game player - and the pleasing thing is both our second rows came through," Lancaster said.
"Geoff had that bang on his shoulder and neither he nor Joe trained on Tuesday. I was pretty confident last night [Wednesday] and this morning [Thursday] we had a lineout session at 8.30am and they were fine.
"It is great for them to play the final game. They have been great for us in this championship."
For the most important team announcement of his tenure, Lancaster's biggest decision was in the back row and he has opted to fast-track Croft back into the starting line-up.
Croft's last start for England was exactly 12 months ago. In April of last year he suffered a triple break to the C6 vertebra and a burst disc when he mistimed a routine tackle on Harlequins number eight Nick Easter.
The Leicester flanker was told later that he had come as close to being paralysed as it was possible to be but he made his comeback for the Tigers on January 4.
After being given medical clearance to play every week, Croft was immediately recalled by England he came off the bench against Italy. Saturday will be his first Test start for 12 months.
Croft will bring a more mobile, athletic dimension to the England back row than the more physical Haskell, who is primed to win his 50th cap off the bench.
"Tom's extra lineout presence will hopefully give us an advantage. He is clearly a quality player and he has had a great impact since he has come back into the team," Lancaster told RFU.com.
"I see it as an 80-minute game. James Haskell's impact coming off the bench will serve us better."
England are chasing their first Grand Slam in a decade and Saturday's clash is a genuine title decider, with Wales capable of retaining their crown.
But Lancaster is yet to lose an away game in the Six Nations and he believes those experiences and the memory of beating New Zealand at home in December will stand his men in good stead.
"They come into game on back of three away wins which is great place to be," Lancaster said.
"They have a very experienced side, around about 600 caps to our 280-odd. They have played in big games and they closed out those Grand Slams (in 2005, 2008 and 2011).
"It will take an outstanding effort but we have done it before, we have been to away games and won. We have played the best side in the world at home and won.
"We go in with a strong self belief. We have won four from four and the New Zealand game as well.
"We have to deal with the occasion and play with composure and accuracy. There is a quiet self-belief."