Saracens assistant coach Alex Sanderson credited his side's battling qualities after beating Worcester 22-12 at Sixways to progress to the LV= Cup semi-finals.
With several key players away on international duty, the Londoners were forced to rely on much of their second-string - 17 points from the boot of young scrum-half Ben Spencer proving crucial.
Towering back rower Ernst Joubert scored Sarries' only try when he rounded off a flowing move and despite Warriors producing a try of their own through Blair Cowan, Saracens held firm enough to top Pool Three and send London Irish crashing out.
"This group of players don't normally play and they are ring rusty, but they did extremely well today as it is now eight out of nine wins for us and this one over Worcester, our bogey team," said Sanderson afterwards.
He added of Saracens' prospects in the Anglo-Welsh Cup, the Heineken Cup and the Premiership: "We want to be greedy and win all three. The best sides in history have won all three and that is what we aim to do."
Worcester head coach Richard Hill was less impressed, adding: "I didn't expect that performance today and I can't really understand it.
"We made a very sloppy start and allowed them to walk in their first try. There were a lot of missed tackles and the first-half performance was not what was required.
"We gave them a soft lead and Saracens are past masters at closing the game out. We picked up in the second half and our attacking game continues to progress but we gave away 19 penalties which is not acceptable."