Tuilagi and Yarde added to England squad
British and Irish Lions rugby union player Manu Tuilagi speaks to members of the media during a press conference in central London on May 27, 2013 - by Leon Neal
The pair will now train with Stuart Lancaster's side but it would be a major surprise if either of them were in the match-day 23 due to be announced by the England coach on Friday.
"They'd have to go some in the next couple of days, it's fair to say," Lancaster said Monday.
"It's a big ask for Manu to come back having had such a long period out.
"He hasn't had any time with us in camp whatsoever, so Tuesday will be the first training session he's done since the Wales game last year."
Powerful centre Tuilagi played 70 minutes in Leicester's 41-18 win against Newcastle last weekend after five months out with a chest muscle injury while Yarde completed his first full game since a hip problem in November during the Exiles' 18-0 English Premiership defeat by Exeter.
England and Wales are involved in a four-way tie at the top of the Six Nations standings with Ireland and France.
The quartet have all won two and lost one of their three matches so far this season but Ireland have a points difference of +42 compared to England's +21, two-time defending champions Wales' +6 and France's +1.