Leicester Tigers flanker Croft will win his second Lions Test cap after scoring two tries on his debut in the 26-21 first Test defeat in Durban. His Tigers teammate Ellis will be looking to make his Lions Test debut after being named on the bench.
Head coach Ian McGeechan has made five changes to the team. Simon Shaw replaces Alun Wyn Jones in the second row and Adam Jones and Matthew Rees come in for Phil Vickery and Lee Mears in the front row. Rob Kearney takes over from Lee Byrne at full-back and Luke Fitzgerald replaces Ugo Monye on the left wing.
Saturday's match will be live on the big screen in the ABC Bar at Welford Road.
British & Irish Lions (vs South Africa at Loftus Versfeld, Pretoria on Saturday 2pm)
Rob Kearney (Leinster and Ireland)
Tommy Bowe (Ospreys and Ireland)
Brian O'Driscoll (Leinster and Ireland
Jamie Roberts (Cardiff Blues and Wales)
Luke Fitzgerald (Leinster and Ireland)
Stephen Jones (Scarlets and Wales)
Mike Phillips (Ospreys and Wales)
Gethin Jenkins (Cardiff Blues and Wales)
Matthew Rees (Scarlets and Wales)
Adam Jones (Ospreys and Wales)
Simon Shaw (Wasps and England)
Paul O'Connell (Munster and Ireland, capt)
Tom Croft (Leicester and England)
David Wallace (Munster and Ireland)
Jamie Heaslip (Leinster and Ireland)
Replacements
Ross Ford (Edinburgh and Scotland)
Andrew Sheridan (Sale Sharks and England)
Alun-Wyn Jones (Ospreys and Wales)
Martyn Williams (Cardiff Blues and Wales)
Harry Ellis (Leicester and England)
Ronan O'Gara (Munster and Ireland)
Shane Williams (Ospreys and Wales)
