Reports in the French media on Friday suggested the fly-half, who has spent his entire senior career with Saracens, would leave for Racing at the end of the season.
Paris-based Racing denied Friday they had reached an agreement with Farrell who, after England's third-place finish at the World Cup last year where he was repeatedly booed by supporters, has taken a mental health break from international rugby and will sit out the Six Nations.
Should England's all-time leading points-scorer head to the French capital, it would make Farrell ineligible for England selection and deal another blow to the Premiership, which has already lost several players to the Top 14.
McCall, speaking after English champions Saracens' 19-10 loss away to Leicester in the Premiership on Saturday, was adamant he wanted Farrell to remain with the North London club but offered little further clarity on his future.
"I think having Owen Farrell in your team is what everybody would want," director of rugby McCall said.
"It's just not fair on anyone to talk about something that is speculation. Until there's something to talk about, we're not going to talk about it."
The former Ireland international, speaking before the game, said he would not begrudge a senior player leaving Saracens.
"I can understand that when players have had long careers at one club, they would want to experience something different," McCall told TNT Sports.
'Led from the front'
Mistakes by Farrell contributed to two of Leicester's three tries, the playmaker throwing an intercepted pass while his kick straight into touch led to another Tigers' score.
Saracens' fifth Premiership defeat of the season meant they had now equalled their total number of losses for the whole 2022/23 campaign, with this result their third reverse in four league games. But they are just a point outside the top four who will contest the title-deciding play-offs following the end of the regular season.
"Owen went well, like he always does," said McCall. "He led from the front and he had a good game. He's very good at putting distraction to one side and we saw that again here."
In the day's other Premiership match, Ollie Sleightholme scored a hat-trick as Northampton returned to the top of the table after a remarkable recovery to beat Exeter 42-36.
The Saints were 26 points down midway through the first half but scored two tries before the interval.
Their England duo of Alex Mitchell and Tommy Freeman then impressed off the bench in the second half as Northampton ended Exeter's impressive run of 23 home matches without defeat.
"Had it been 26-0 at half-time you are talking about a mountain to climb, whereas 26-14 at least you are saying 'we've hurt them and you can create some belief around it'," said Saints supremo Phil Dowson.
