The Lions hit the half-way mark of their 10-match tour in Sydney yesterday and marked it with a fifth successive win, 47-17, over the HSBC Waratahs. But they picked up another worrying injury, this time to Test centre Jamie Roberts.
Billy Twelvetrees and Christian Wade have already been called out to Australia from England's tour in South America, while Ireland's Simon Zebo arrived last week in time to make his debut at the Allianz Stadium last night.
But with Roberts due to have a scan on his injured leg today, and Manu Tuilagi and George North still troubled by shoulder and hamstring problems, the Lions have taken the precautionary measure of recruiting another player.
Barritt's staunch tackling and organization has seen him become the cornerstone of England's defence having played in 16 of their last 17 Tests up to the end of the RBS 6 Nations Championship.
He made his international debut, alongside Saracens team-mate Owen Farrell, against Scotland at Murrayfield last year and he started every game in the 2012 Championship. He went on to play twice against his native South Africa during the summer tour, but had missed the second Test after an operation to repair a lacerated eyeball.
The climax to Brad's four starts in the November internationals was his maiden Test try in the record victory over New Zealand at Twickenham. His defensive attributes came the fore when England beat Ireland 12-6 at the Aviva Stadium in this year's 6 Nations and he excelled against France at Twickenham.
A former vice-captain of the Sharks in Natal, Barritt helped the Emerging Springboks, to lift the IRB Nations Cup in Bucharest in 2007. However, he was offered the chance to join Saracens in November 2008 as well as complete his Business degree.
Barrritt scored a try on his full debut against Bristol Rugby in January 2009, when deputising for now British & Irish Lions defence coach Andy Farrell, and was selected for England Saxons's Churchill Cup campaign in USA that summer.
He went on to be named Saracens Player of the Season in 2009-10 and his progress was so rapid that he was called from the 2010 Saxons squad into England's senior party to Australasia as cover for Dominic Waldouck, appearing in the non-cap match against New Zealand Maori at Napier in June that year.
Born in Durban, Barritt's grandparents were from England and his grandfather represented English Universities.