The Munster and Ireland prop jumped at the chance and arrived in Durban over the weekend, eager for some game-time with his last appearance for Munster back on May 10 in a Magners League game against the Cardiff Blues.
Fitness wise Hayes is is 'good fettle', according to Lions team doctor James Robson, and having been called up in place of the injured Euan Murray, he has been pencilled in to start Tuesday's tour match against the Emerging Springboks.
Ahead of his first Lions appearance since a hard-fought win over Auckland on the 2005 New Zealand tour, he said: "Yeah, I can't wait for it. Delighted to get the call. I was lucky enough that there's a midweek match left, so I'm getting the chance to play."
Hayes was admittedly disappointed at missing out on a place in the initial Lions squad, but did he hold out hope that he might be called up as a replacement at some stage?
"It's hard to be hopeful, because unfortunately it means misfortune for someone else.
"Anybody that's been called out has always been called out for someone that's been injured - you can't be hoping that something like that is going to happen.
"Unfortunately, it does happen and I'd commiserate with Euan. It's the nature of the tours, long tours like this with a lot of games. When I did get the call, I was delighted."
Hayes has never been a player to shirk a challenge, with 94 Ireland caps and Grand Slam, Heineken Cup and Magners League successes behind him.
Being part of a Test series-winning Lions side would be another proud achievement for the 35-year-old, but forcing his way into Ian McGeechan's Test team is not something he has allowed himself to consider just yet.
"I'm not looking that far at all. I haven't played for a few weeks, just got out here at the weekend so I'm just looking no further than Tuesday night.
"I'm delighted to get the chance to play for the Lions again and that's all I'm looking at at the moment."
Hayes watched the first Test and was impressed with the Springboks and 'the huge start' they made.
"They were in camp for a number of weeks and they will have been going through videos, watching stuff, building up for the game and they just came out of the blocks at 100 miles an hour."
'These things happen' was Hayes' verdict on the scrummaging problems that Phil Vickery and company encountered in Durban, with South African loosehead Tendai Mtawarira given most of the credit for the pressure put on the Lions scrum.
So what does 'the Bull' make of 'the Beast'?
"I've never played against him. I haven't played against South Africa for a few years now. 2006 was the last time.
"He wasn't playing then, he's only come into the side in the last couple of years.
"He's made a big name for himself in Super 14 rugby, as an all-round player, ball carrier and scrummager.
"He looks to be taking over from Os du Randt and he's been a serious contender for top loosehead," added Hayes.