Hastings will win only his fourth cap, with Racing 92’s Finn Russell unable to play as the game falls outside World Rugby’s international window.
The 22-year-old Hastings’ previous three Test appearances came on Scotland’s summer tour against Canada, the United States and Argentina. Gatland put the focus firmly on Hastings at his pre-match press conference by saying “we have got to make sure we put as much pressure on him as we possibly can”.
But McInally responded: “Adam’s been playing really well for Glasgow. Since he’s come on the scene he’s shown a lot of potential and been earning his stripes.
“He played very well on the summer tour, especially in that last game against Argentina. We’re really excited to see him play. He works very hard on his game and he’s got a lot of confidence that he can go out and express himself.
“In training he’s been very vocal as well, which is important for a ten.”
Scotland have not win in Cardiff since 2002 and have lost on their last nine visits to the Principality Stadium - the latest being a 34-7 defeat nine months ago.
“Going back to that game in February, we started poorly,” McInally said. “Wales played really well that day and we weren’t at our best.
“We know the challenge that faces us, they’re physical and when they get the crowd behind them here they’re a very hard team to beat.
“But we’ve got our strategy in place that we think we can come here and win.”
The two teams will compete for the inaugural Doddie Weir Cup, with the Welsh and Scottish Rugby Unions donating a six-figure slice of the gate money to the former Scotland second-row forward’s foundation.
Weir is suffering from Motor Neurone Disease and the 48-year-old was at the Principality Stadium on Friday to see the Scotland team run.
“It’s the first time we are playing for the Doddie Weir Cup and he’s an inspirational guy,” McInally said.
“It was nice to see him here and the boys do take a bit of added inspiration from that.
“We want to put in a performance that everyone is proud of, especially him.
“We’ve been building towards the World Cup for the last couple of years, but this is the home run into it now.
“We’re very aware of the number of games we have until the World Cup, but there’s a lot of rugby to be played before then and it will be good to get off to a good start.”