Donnelly (29) will play his first and only game in the blue and gold jersey this season when the side takes on Auckland tomorrow.
His last game was more than a month ago, for the national side against Australia in Sydney, but he said an early return to Otago was not an option.
"I'd really like to play as many games as I could for Otago. 0I'd like to play every week. But logistically that is not possible," Donnelly said.
"I had niggles and wee injuries and you need to get on top of them. My foot [that] I hurt at the start of the year was playing up."
Donnelly said the past three weeks was like going through a pre-season again, with the amount of training he had done. He had gained 4kg, as the All Black selectors wanted him to put on weight and increase his strength.
He was looking forward to getting back on the park, and contributing as much as he could to the Otago cause.
"You just have to see how they [Otago players] train and then watch them play that they are trying their guts out. But the guys are finding it tough, and that happens sometimes in sport.
"I think some of it comes down to a lack of experience. We had a meeting the other day and of the five most experienced guys there only one of them was playing.
"But I'll be doing as much as I can. Leading from the front and helping out."
Donnelly had some down time over the past month and did some hunting and fishing.
Reflecting on the All Black season, he said the senior players and coaches had stepped up, and less experienced players, himself included, had followed along.
"I was a bit nervous leading into the season, coming off the injury and that, but everything just worked out.
"We had quite a lot of confidence from the senior guys and the coaches and they really lead the team round the paddock. It was fun but then it always is when you're winning all the time."
While he was a fixture in the All Black second row this season after getting over an ankle injury, Donnelly said he was no certainty to make the side to tour the northern hemisphere.
He had the game against Auckland to concentrate on first and said the side had the added motivation of playing for the Lin Colling Memorial Trophy.
"That is a huge incentive for the guys. The Collings are a huge Otago sporting family so we want to do well for them."
Donnelly had re-signed with Otago and the Highlanders until 2012 and he said he was excited about the changes in the Highlanders.
Otago does not have a great record at Eden Park. It last won there in 1976, and last beat Auckland in 2003.
Along with Donnelly coming into the side for Josh Townsend, Paul Grant takes over at No 8, replacing Charlie O'Connell, who drops to the Otago B side.
Chris Small is still off colour after picking up gastroenteritis so Joe Hill is at fullback and Ryan Shortland on the right wing.
Cromwell product Scott Manson is on the bench and the prop will make his Otago debut if he gets on the paddock. Blair Young has a sore back and Kees Meeuws is still nursing a knee injury.
Auckland welcomes back Isaia Toeava to the starting side after he come off the bench last week to spark a win over Counties-Manukau.
Former Otago halfback Toby Morland also comes back into the Auckland team.
OTAGO v AUCKLAND
- Tomorrow 2.35pm, Auckland
Referee: Kane McBride (Canterbury)
TAB odds: Auckland $1.05, Otago $8.
• Otago: Joe Hill, Ryan Shortland, Josh Tatupu, Glenn Dickson, Fetu'u Vainikolo, Chris Noakes, Sean Romans, Paul Grant, Alando Soakai (captain), Hoani Matenga, Hayden Triggs, Tom Donnelly, Halani Aulika, Peter Mirrielees, Sam Hibbard.
Reserves: Wyatt McKay, Scott Manson, Seko Kalou, Brad Cameron, Johnny Legg, Paula Kinikinilau, Andrew Parata.
• Auckland: Brent Ward, Dave Thomas, Isaia Toeava, Benson Stanley, Joe Rokocoko, Gareth Anscombe, Toby Morland, Peter Saili, Daniel Braid (captain), Onosa'i Auva'a, Andrew van der Heijden, Kurtis Haiu, John Afoa, Ash Dixon, Charlie Faumuina.
Reserves: Tom McCartney, Angus Ta'avao, Liaki Moli, Sean Polwart, Brenton Helleur, Mathew Berquist, Winston Stanley.
