There are times when even Scott Johnson knows that a bit of discretion is required.

When asked on Saturday evening if he expected that coaching a winning team this week would be a lot easier than trying to deal with one that had just lost, a larrikin grin spread across the Australian's face as he shaped his reply. "Well," he said, "it's a bit like coming home to a happy wife."

Fortunately, and just before the colour drained completely from his media minder's face, the Scotland coach decided for himself that the analogy could be left there. Johnson muttered something about happy households and quickly returned to the safer ground of his technical dissection of the team's performance.

As comfortable as this victory was at the end, it left a lot of questions unanswered.

Should Johnson be happy with his scrum because of the damage it wrought in the first half, or furious because of the damage it sustained in the second?

Should he be filled with confidence by the six smart tries Scotland scored, or dread by the two they gifted to Japan?

His dilemmas were apparent even in the immediate aftermath, when even he struggled to come up with a consistent or vaguely rational explanation of what he had just seen.

It was only a while later that things seemed to be falling into place. "There was more good than bad," concluded Johnson, an observation that will be more illuminating still when he figures out where the boundaries between those categories should lie.

Over the next few days he will, unquestionably, want to focus much of his attention on the defensive frailties Japan exposed with their slick running. But he will also know the danger of falling into the old generals' trap of fighting the war just ended, well aware that South Africa, next Sunday's visitors to Murrayfield, will take a very different tack to the one Japan followed. This may have been a hard match in many regards, but in terms of raw brutality it was not remotely close to what the Springboks will serve up.

That much would have been obvious to any Scotland supporters who made their way home from Murrayfield, parked themselves in front of the television and watched South Africa's 24-15 victory over Wales at the Millennium Stadium. Talk about a meaty main course after a light starter. There was an intensity about the contest in Cardiff that was many notches above anything seen in Edinburgh, and that has to be the focus of Johnson's deliberations over the next few days.

"We have to be honest and accept there are some issues," he said. "If we do a couple of those things against the big boys next week? Phew, we are in trouble. The beauty of that victory for us was that there are still plenty of things we need to work on. For a coach, that is a win-win situation."

In selection terms, he knows already that he must change his front-row, Euan Murray being unavailable for Sunday's game on account of his religious beliefs. And he will surely make a change at lock, where Richie Gray seems set to take over from Al Kellock. Johnson may have entertained thoughts of a completely new second-row, with Jim Hamilton coming in as well, but Tim Swinson's man-of-the-match performance will almost certainly have dynamited that idea for the moment.

With Matt Scott looking doubtful on account of the hand injury he picked up late in the game, Johnson may have to examine his midfield options as well. With Alex Dunbar probably ruled out too, and with Peter Horne expected to miss the entire season, the easiest option for the coach would be to bring Sean Lamont in from the wing, with Duncan Taylor taking over the berth he vacates. However, Mark Bennett and Max Evans are also in the squad, so either could be called upon to do a shift against the Springboks.

Johnson indicated that the fact he must send out a side against Australia less than a week after the South Africa game may also have a bearing on his thinking. "I have thought about it, clearly," he said. "We have a six-day turnaround before Australia. I have to manage this now. There is no point having boys in the squad if I don't see what they are like."

Johnson had to be pleased with the way Scotland put away their chances. Yes, perhaps they could have done more on that front, but this was the first time they had scored more than five tries in a game since 2008 - when they claimed six against Canada - so it was not an achievement to be sniffed at. That five of Saturday's six tries came from backs reflected the broken pattern of the game, particularly in the final quarter. That said, the try that produced the deftest handling passage was the one collected by replacement prop Ally Dickinson, who was put through by fellow forwards Al Strokosch and Ross Ford.

Tommy Seymour could be happy with his brace, while the others fell to Greig Laidlaw, Duncan Weir and, perhaps most deservedly, Sean Lamont. Japan's brilliant young winger Kenki Fukuoka capped his electrifying display by claiming both their tries. Astonishingly, Fukuoka is still a college player and has not yet played for a professional club. He will have no shortage of suitors when he decides to make that move.