The 34-year-old second row is hoping to go one step further this term as Sarries look to add the Heineken Cup trophy to the English title they won in 2011, although defeat to four-times continental kings Toulouse at Wembley last month has put them on the back foot in Pool 3.
Borthwick will be at the heart of their quest to bounce back from that disappointment with successive wins over Zebre on December 7 at the Stadio XXV Aprile and again a week later at Allianz Park but he has turned down the chance to carry on playing next season.
The former England international, who captained his country between 2008 and 2010 and wore national colours on 57 occasions over nine years, was offered a new contract but instead decided to quit while he is still in fine form.
"Very few players have the chance to retire on their own terms," said Borthwick. "Saracens did ask me if I'd like to carry on but I feel that the time is right for me to finish playing at the end of the season.
"That's still a few months away, and I am obviously 100 per cent focussed on improving as a player and leading this team to the best of my ability."
Borthwick has played 253 times in the top-flight of English Rugby with Saracens and previous club Bath and has made 88 appearances in Europe. A half century of those have been Heineken Cup starts, with two more coming as a replacement and another 36 being in the Amlin Challenge Cup.
He led Bath to Amlin Challenge Cup glory in 2008 and is highly respected across the game, no more so than by his current employers, for whom he has been instrumental in their rise to the top echelons of the European game.
"Steve has become a Saracens legend, as a leader, as a player, as a man who sets the highest standards in everything he does," said Saracens director of rugby Mark McCall. "He will be sorely missed in due course but, for now, with Steve at the helm, we are focussed on Saturday's match against Sale."