Owen Farrell, 20, was man of the match with 22 points as Saracens beat Treviso 42-17,but for McCall the real eye-catcher was replacement scrum-half Ben Spencer, who came on for former Springbok Neil de Kock.
"Owen deserved to be named man of the match, but I was very impressed also by Ben, who came here only three months ago from Cambridge Rugby Club on a training contract," McCall said.
"It was initially to make up the numbers, but he is now on a contract beyond the end of this season and has just turned 19.
"That was his first taste of European rugby yet he looked comfortable in all that he did.
"When Richard Wigglesworth's injury ruled him out for the rest of the season, we decided not to sign any other cover at scrum-half. That's a measure of how well Ben has performed since arriving."
James Short is another academy product delighting McCall, who added: "This lad has had a big 12 months and gets better and better with games. I believe he is making tremendous progress."
Saracens may be early pool leaders, but the club's decision to play their other two 'home' Pool Five games away - against the Ospreys at Wembley and Biarritz in Cape Town - has divided opinion.
McCall admitted: "Dealing with things coming at you from left field at Saracens is nothing new and is what makes this club that bit different.
"I believe the boys will really enjoy going back to Wembley and they'll love playing in Cape Town."
McCall also feels that former South Africa World Cup winning captain John Smit will enjoy himself after making a try-scoring debut off the bench.
"After six or seven years of leadership duties and responsibilities, John just wants to play rugby again," McCall said. "What he brings to the squad does not require detailing in terms of ability and experience."
Smit added: "That was my first game as a non-captain for some time and it was enjoyable. Right now I am more worried about getting the calls right than anything else.
"It was good to come on, good to score a try, but getting the bonus point was what was most important for the guys.
"We see the Heineken Cup on television back home and it is very highly rated and enjoyed. I had a brief spell in France with Clermont and I have played at Biarritz before, so we have our work cut out there next weekend.
"There are some very exciting young players here. I think in the case of Owen Farrell for example, England selection is a case of when not if, and there are other lads equally impressive."
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