Villeneuve and Frentzen are understood to have felt the force of Head's displeasure in recent weeks as they have struggled to keep pace with the championship leader, Ferrari's Michael Schumacher.
Frentzen in particular has looked ill at ease against his German compatriot and desperately needs to recover both ground and reputation in his home grand prix here tomorrow.
Another shambles on the scale of his performance at Silverstone a fortnight ago may challenge the patience of Head and Frank Williams beyond constraint and reinforce conjecture he could be released at the end of the season.
Even Villeneuve, trailing Schumacher by only four points in the drivers' standings, has frustrated Head with his limited technical feedback and both drivers have expressed differences of opinion with their bosses over settings. Head, however, chose to respond to questions over apparent rifts with what amounted to a vote of confidence in the drivers. He said: "As far as I understand, the drivers we have now will be our drivers next year.
"Heinz-Harald has a two-year contract and I understand we have taken up our option on Jacques. I'm more than happy with our drivers at the moment and don't consider we'll make a change next year. Both are very quick.
"What happened after Silverstone is an internal matter. Contrary to popular belief, Heinz-Harald is not being invited to the factory for a whipping. We are more interested in looking forward."
Frentzen had talked 24 hours earlier about a clash of opinion with Head on technical matters and indicated part of the problem lay in the generation gap between them.
"That is understandably a factor and makes it more difficult to relate well, but our race engineers and technicians are close to the driver's age and they can relate," Head said. "It's a problem of life, not one restricted to motor racing."
But perhaps he and Williams had re-evaluated Damon Hill and developed misgivings about their decision to unload him at the end of last season?
Head padded the teaser. "Damon was a just and worthy world champion and I have never thought of him in any other way. He is a very fine driver but through certain circumstances he is not driving for us in 1997."
For all the evident vulnerability of the Williams' line-up, Head backed his men to take Schumacher to the line, although he pulled up short of predicting ultimate success.
"I'm not a betting man, but I still feel very positive and confident that if we get the best out of the equipment we have we can take a good fight to Michael in particular and Ferrari in general," he said.
"Only once this year have we finished a race with two cars, so it has certainly been a weak year in relation to what we want to achieve. It is a question of making as few mistakes as possible."
Head admitted his team were having to compromise their effort on the current car to work on next year's. "Few of us have unlimited resources," he reasoned, which might be interpreted as an allusion to Ferrari's funds.
Williams' plans for 1998 seemed distinctly clearer than those of Benetton, who have yet to find - or at least announce - their solution to Renault's official withdrawal from Formula One.
They must also name a partner to Giancarlo Fisichella. Gerhard Berger has confirmed he will leave the team while Jean Alesi is expected to follow him, and be replaced by Alexander Wurz.
Flavio Briatore, the team principal, managed merely to cloud the issue, saying he had his drivers already for next year, then stating he had made no decision. He would also reveal his engine deal when he was good and ready and not before.
Mercedes have one of the stronger, if not the strongest, engines in grand prix racing and McLaren's partners admit they would like a Schumacher on board. Alas for them, Michael and Ralf are otherwise engaged for at least another year.
David Coulthard is keen to secure his place in the team for another season and believes a win here tomorrow would effectively achieve that objective.
The Scot had little opportunity to prepare for his race yesterday in a practice session spoiled by rain and he recorded only the 17th-fastest time.
Ralf Schumacher (Jordan-Peugeot) and his brother were first and second respectively, and Britain's Johnny Herbert third in a Sauber-Petronas. Hill (Arrows-Yamaha) was ninth, Eddie Irvine in the second Ferrari 10th, Villeneuve 16th and Frentzen 18th.
GERMAN GRAND PRIX (Hockenheim, tomorrow) Practice times: 1 R Schumacher (Ger) Jordan-Peugeot 1min 46.196sec; 2 M Schumacher (Ger) Ferrari 1:46.322; 3 J Herbert (GB) Sauber-Petronas 1:46.517; 4 R Barrichello (Bra) Stewart- Ford 1:46.526; 5 N Fontana (Arg) Sauber-Petronas 1:46.706; 6 P Diniz (Bra) Arrows-Yamaha 1:46.873; 7 S Nakano (Japan) Prost-Mugen-Honda 1:47.143; 8 M Hakkinen (Fin) McLaren- Mercedes 1:47.386; 9 D Hill (GB) Arrows-Yamaha 1:47.542; 10 E Irvine (GB) Ferrari 1:47.594; 11 J Verstappen (Neth) Tyrrell-Ford 1:47.720; 12 J Magnussen (Den) Stewart-Ford 1:47.769; 13 J Trulli (It) Prost-Mugen- Honda 1:47.784; 14 G Berger (Aut) Benetton-Renault 1:47.887; 15 J Alesi (Fr) Benetton-Renault 1:48.455; 16 J Villeneuve (Can) Williams-Renault 1:48.639; 17 D Coulthard (GB) McLaren-Mercedes 1:48.648; 18 H-H Frentzen (Ger) Williams-Renault 1:48.958; 19 G Fisichella (It) Jordan-Peugeot 1:49.010; 20 T Marques (Bra) Minardi-Hart 1:49.563; 21 M Salo (Fin) Tyrrell-Ford 1:49.831; 22 U Katayama (Japan) Minardi-Hart 1:51.058.