The Radio 2 breakfast show host and Friday evening One Show co-presenter told his Twitter followers that he is on call and ready should Corden lose his voice.
However, Corden joined Evans on air as planned for a pre-Brits interview on Wednesday morning (February 20) and confirmed that he was recovering from illness, but had actually felt far worse last weekend.
"Just been declared official Brits stand by host/understudy. In case James's voice doesn't make it to the Lifetime Achievement award," Evans had wrote. "Now - how to nobble him. In a nice way of course."
It was reported yesterday that Corden was sent home from rehearsals yesterday after contracting tonsillitis, although a spokesperson for the Tony Award-winning actor said that the severity of his illness had been "greatly overplayed".
Evans - who has been sharing his favourite Brit Awards memories with listeners on his Radio 2 show this morning - was joined in the studio by Corden after the 8am news.
Corden said that he felt "absolutely fine" when Evans introduced him on air by noting that he looked "a bit peaky", and read out contributions for the show's 'Listener Breaking News' feature.
The comedian also teased Evans by saying that the organisers wanted him to present a Brits trophy, saying: "If you're gonna come down and wait in the wings, you're gonna have to give one [award] out."
Corden is due to host the Brit Awards for the fourth time at tonight's ceremony, which takes place at London's O2 Arena.
Brit Awards - the most memorable moments - photo gallery:
Copyright: Eugene Adebari/Rex FeaturesWatch Little Mix, Labrinth and Ed Sheeran chat to Digital Spy at the Brit Awards below: