IF Katherine Grainger is going to claim a fifth Olympic medal to round off her collection of rowing souvenirs, then it seems likely to come via the hardest of routes. Not that the Scot ever thought it was going to be easy, given a build-up to these Games that brought an unfamiliar spot outside the medals at the European Championships in the spring, and an early-summer spell wondering if she and double- sculls partner Vicky Thornley would even be selected for Rio.

But in opening the defence of the crown won in such exhilarating fashion at London 2012 in tandem with Anna Watkins, the 40-year-old betrayed a level of fallibility that might see her reduced to the ranks of the mortals.

With the statue of Christ the Redeemer casting a shadow over the hills that surround the Lagoa Stadium, the British pairing were elbowed out of the limelight by Donata Vistartaite and Milda Valciukaite, who hauled back a deficit before sweeping past to take victory in their initial heat.

It is not as if the Lithuanians do not have a certain pedigree. Winners of World Cup stops in Lucerne and Varese, they will assuredly be in the mix when the medals are determined on Thursday. But after attempting to assert themselves, Grainger and Thornley were instead dominated, with the French crew of Helene Lefebvre and Elodie Ravera threatening to also sneak by.

All three boats advanced into Tuesday’s semi-finals, but you wonder what psychological blows have been struck.

“The Lithuanians are a very good crew,” Grainger said. “We were very pleased with our start. Those conditions are pretty challenging in the middle. It’s probable that they handled them better than we did.

“We are not under-cooked after missing two World Cup stops in a truncated build-up. I don’t think it’s had a massive effect. We do a lot of training and racing behind the scenes within our own team. We’re still race-ready and race fresh.”

Inverness-born rower Alan Sinclair safely advanced into the semi-finals of the pairs with Stewart Innes by coming second in their heat behind France’s Germain Chardin and Dorian Mortelette.

However, their fellow Scot Angus Groom will need to take an even more circuitous tour to the podium after the British quad sculls were surprisingly tipped into the choppy waters of the repechage by coming fourth in an opening heat in which only 1.79 seconds separated them from the victorious Australians.

John Collins and Jonny Walton will likewise have to rely on the repechage in the double sculls after they came fourth in their heat, but London 2012 bronze medallist Alan Campbell eased into the quarter-finals of the single sculls.

“I’m very happy,” the Northern Irishman said. “It was pretty tough conditions out there, pretty choppy, but I’ve dealt with it well and got myself across the finish line first.”

Meanwhile, Heather Stanning claims there is less pressure on her shoulders than in London four years ago as she and her partner Helen Glover prepare to start the defence of their pairs crown today. In the interim, the Lossiemouth woman took a season to return to her military career, but results since have taken a load off their minds.

“We’re quite happy with where we’re at the moment,” she said. “We’ve travelled well, we’ve got a feel for Lagoa. There’s a lot going on but it’s exciting, and we’re excited to get racing as well.

“We’ve had fantastic training camps. We’ve had a good year. We’ve done everything we can do. We just hope now it was all we needed to do.”