Worcester centre Josh Matavesi made the challenge on De Kock which so incensed McCall he remonstrated with Worcester counterpart Richard Hill.
"It was a horrendous challenge; we could have lost our scrum-half with a broken jaw or cheekbone," said McCall. "Fortunately he seems to be ok but it looked pretty deliberate to me; I leapt up as I felt it could have been a deliberate game ploy from Worcester."
Hill, who accepted that the tackle was bad, said: "It was a very clumsy challenge from Josh but he's not a malicious player.
"It was badly mistimed and a citing seems likely. Josh has apologised and I fully understand Mark's reaction to protect his player."
Saracens were able to record a convincing win which secured their home semi-final spot despite resting a number of key players.
McCall added: "It showed the depth of our squad as we backed up well after a testing European quarter-final at Twickenham.
"We took our chances, David Strettle's second try was as good a finish as you will see but though we are happy with the win, we played well below our standard."
Worcester continued their disastrous away record in the Premiership and could not recover from being 23-3 down after only 25 minutes.
Hill said: "We had a very poor slow start but got our second wind just before half-time and they were a bit rattled when we got it back to 27-17. We didn't deserve to lose by such a big margin as we gave away two soft tries at the end, trying to run from an impossible position."
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