England centre Billy Twelvetrees has been called into the Lions squad as cover for injured trio Owen Farrell, Manu Tuilagi and Johnny Sexton.
Sexton has a hamstring problem and Farell has a dead leg, injury which forced the fly-half pair to miss the fourth win of the tour against a Combned County's XV on Tuesday. Tuilagi meanwhile was replaced early in the win over Queensland Reds with a shoulder problem.
Stuart Hogg was forced to deputise at No.10 for the Lions and Twelvetrees, who becomes the fourth call-up since the tour began following Ryan Grant, Alex Corbisiero and Simon Zebo, represents a back-up should any of the trio not recover from their respective injuries.
"The nature of a Lions tour means that there will inevitably be knocks which take time to recover from," coach Warren Gatland said. "The whole squad have worked hard but a lot of the backs have doubled up over the last two games, either starting or from the bench. Billy played well in the 1st Test for England and he provides that versatility to cover a variety of positions."
Both Tommy Bowe, who has a hand injury, and Rob Kearney remain doubts with just two games to go until the opening test against Australia in Brisbane.
Twelvetrees leaves an England squad who romped to a 32-3 victory over Argentina on Saturday, with the Leicester centre running in one of four tries in Salta.
The 24 year old made his international debut in the Six Nations win over Scotland at 12, but could be used at 13 or 10 during the tour, with the Lions lacking options with a gruelling schedule taking its toll.
After the win 22-12 weekend win over the reds, Gatland had said: "We have to make sure they [injured players] are right
"Jonny will have to play again before the first Test.
"Given that both fly- halves have been involved in every game, we are at the stage where we have to look after them and give them an opportunity for a rest."
Defence coach Andy Farrell added:"Like every game of rugby, guys have got little knocks and tweaks, but there is nothing serious.
"Owen has a bit of a dead leg, that's all, so that is precautionary. Jonny was just a little bit tight (hamstring), but he's fine as well.
"They have to recover properly, especially with the flights, so they had training off today, but they are fine.
"Rob Kearney trained this morning and he ran very well. He will be back with the boys tomorrow morning, and he will be looking to be fit for the weekend."