Saracens crashed out of the Heineken Cup with a comprehensive 22-3 quarter-final defeat to the star-studded French giants Clermont Auvergne.
For only the third time in the history of English clubs' involvement in the Heineken Cup there will be no Premiership representatives in the semi-finals.
Clermont will tackle Leinster and Ulster face Edinburgh for a place in the Twickenham final.
Exeter, Harlequins and Wasps, who are all required to operate within the Premiership's £4.2million salary cap, lost to French opposition in Amlin Challenge Cup quarter-finals this weekend.
Director of rugby McCall said: "You could almost see the difference in the salary caps as you looked down on the pitch at various times today, there is no question about that.
"The squad they were able to bring is outstanding and the stats don't lie. It is getting increasingly difficult to get into the quarter-final stages.
"For England to have absolutely no involvement in the semi-finals of the Amlin or the Heineken Cup speaks for itself."
The French Top 14 operate a salary cap but it is far greater than that agreed by Premiership Rugby, the English clubs' umbrella body.
Clermont coach Vern Cotter does not believe the result, which saw his side overpower the Premiership champions, was down to the salary.
"There is a salary cap in France as well, it is probably slightly more elevated than it is here. I don't believe that was the reason for the result today," Cotter said.
McCall conceded that, on the day, his side had been distinctly second best as Clermont fly-half Brock James kicked 17 points while Lee Byrne scored the only try of the afternoon.
"Today we came up against an outstanding team who played a great game," McCall said.
"I was a little bit surprised (how much more physical Clermont were than Saracens). This stage of the competition is a step up to what we are used to.
"Their team is star-studded and the internationals they brought off the bench, they were just too good for us today.
"They will be a very difficult team to beat. Their semi-final against Leinster will be tremendous."
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