Beattie sat out the Scots' final training session in Johannesburg yesterday. The official explanation for his absence was that the 27-year-old Montpellier forward has been carrying a thigh strain, but there was a suspicion that the purpose of that bulletin might be to divert attention from the shoulder injury he picked up against Samoa two weeks ago.
If Beattie does have to withdraw then his place in the starting lineup will go to Rob Harley, although Harley is likely to play at blindside, with Dave Denton switching to No.8.
Fraser Brown, the uncapped hooker who was named among the replacements on Thursday, will have his remit changed to cover the back row, with fit-again Steve Lawrie promoted to the bench to cover the hooking role.
"We have no-one else, so we're going to give Johnnie until the warm-up," said Johnson. "I'd say he's 50/50 at the moment, but he's a tough lad. Everyone talks about his skills, but his rugby is tough as well. He's resilient and he's played injured before.
"Last week he had a bad wing [shoulder] but I thought he tackled superbly, so he has the ability to put it out of his head. So we'll go late with it, one because we have no choice and two because he's got the character we think can carry it."
Johnson has made no secret of his admiration for Beattie since he took over as interim head coach last December. Whereas Andy Robinson, Johnson's predecessor, had all but eliminated the former Glasgow Warrior from his thinking and his plans, Johnson recognised that Beattie's form and appetite had been rejuvenated by his move to France the previous summer, and duly picked him throughout the Six Nations.
Today's match with Italy is the Castle Series' third/fourth play-off, with Scotland starting as modest favourites on the strength of their 34-10 Six Nations victory at Murrayfield a few months ago, their slightly higher (11th v 12th) position in the world rankings, and their more combative outings, against Samoa and South Africa, in the quadrangular tournament to date.
However, having stressed the value of the current visit to South Africa in terms of developing players for the future, Johnson, who will devote himself to his duties as national director of rugby when his period as caretaker coach is over, suggested that he wants to see Scotland return to a more traditional kind of tour, with multiple matches against top opposition.
Although the details are yet to be confirmed, Scotland's schedule for next summer is a mind-addling itinerary that will take them to Canada, the USA, Argentina and South Africa. It is understood, however, that efforts may be made to drop some parts of the tour, with the matches in North America most likely to fall off the agenda.
"I'll be arguing to bring on the big boys as often as we can. Yes, there will be times we're on the wrong end of the scoreboard, but the self-belief will grow. If we keep working on the things we need to work on, and keep improving, we'll keep knocking on the door."
Peter Horne, the Glasgow centre who made his Scotland debut against Samoa two weeks ago, will miss much of next season after scans of the knee injury he suffered against South Africa last weekend revealed cruciate ligament damage. The 23-year-old is expected to be out for nine months.
However, the knee injury suffered by the Glasgow hooker Pat MacArthur is less serious than first thought. He should be fit to play again at the start of the new season.