Lions defence coach Steve Tandy believes Bundee Aki will have a key role to play in the defensive system he looks to implement over the coming weeks in South Africa.

Aki has wasted little time in making his presence felt in the Lions squad, with out-half Dan Biggar revealing that the Connacht and Ireland centre set the tone in an early training session with a thumping hit.

The 31-year-old will start alongside his close friend Robbie Henshaw in tomorrow's opener against Japan at Murrayfield, with Tandy excited about what Aki can bring to the party.

“Oh, he has been outstanding,” Scotland's defensive specialist said.

“He has been great. I know it sounds that I've got to say it, but every player that has come in, they have been fantastic to work with.

“It has been a real pleasure for me to see how quickly boys take up messages and how fast they move. They are absolutely quality within the squad.

“But Bundee has been excellent. You see him and Robbie Henshaw working around hand-in-hand together a lot of the time, so they are pretty connected as well.

“You see those boys getting ready to play at the weekend and I'm just really excited to see them go.”

Asked about Aki's ferocious tackle in training, Tandy was keen to stress that while the Ireland midfielder will bring a natural physical edge, he has many more strings to his bow.

“Yeah look, we had a little bit of a live (session) and you could see there was no quarter given in there. Everyone is going for it,” Tandy said.

“Bundee, obviously that is a real strength of his, but I also think with Bundee, his foot movement, his actual reading of plays as well is absolute quality.

“But in fairness, everyone has come in, the quality of the physical contact and things in training, we haven't had obscene amounts of it, but you can see the mindset is really positive.”

Tadhg Furlong's late promotion to the Lions team means that all seven Irish players will start against Japan tomorrow.

Tandy has been impressed with Furlong's attitude, as he looks to bounce ideas off the Ireland tighthead, who is embarking on his second Lions tour.

“It has been awesome to work with Tadhg,” Tandy added.

“It's been unbelievable to work with all these players. I think they are all really good blokes, they are all keen to share and chat.

“But Tadhg is really impressive. As a tighthead prop obviously, scrummaging, which I don't know a lot about, but in and around the park, for a big man, he moves really well.

“He understands the game and it has been really good to chat with him about how he sees defence and things. He has been a real pleasure to work with.”