Ireland hooker Rory Best has been called into the British and Irish Lions squad for the tour of Hong Kong and Australia.
The Lions turned to Best after Dylan Hartley was banned for 11 weeks after being found guilty of verbally abusing referee Wayne Barnes in the Aviva Premiership final.
A final decision on Hartley's participation in the Lions tour will be dependent on the outcome of any potential appeal.
Best, who had been appointed Ireland captain for the summer tour of north America, will link up with the Lions tomorrow ahead of their flight to Hong Kong.
The Lions play their first match against the Barbarians next Saturday and tour manager Andy Irvine said: "With uncertainty over the availability of Dylan Hartley to tour, and with the first of 10 matches only days away, we had no option but to call up the additional player.
"Despite the circumstances we should congratulate Rory, who will join the squad tomorrow and fly with us to Hong Kong.
"A final decision on whether Dylan Hartley will take any part in the tour will depend on the outcome of any potential appeal."
Northampton are understood to be waiting until they receive the full written judgement from Judge Jeff Blackett, the RFU's chief disciplinary officer, before deciding whether or not to appeal.