The flanker is now a major doubt for the Six Nations showdown against England after hobbling out of Wasps' six-try destruction of Northampton.
The flanker was the only current Ireland player to start a domestic game this weekend while the rest of his team-mates were rested ahead of next Sunday's encounter in Dublin.
And he limped out of the Zurich Premiership game in the 55th minute with an injury to his left ankle that opens the door to Munster's Denis Leamy to reclaim his place in the back row.
By the time O'Connor left the field, though, Wasps were over the horizon and hammering a hapless Saints side thanks to Voyce's hat-trick, a try from Matt Dawson and a brace from Mark van Gisbergen, who also added a penalty and three conversions.
Northampton, who hauled off both half-backs before the break, replied with two penalties from Paul Grayson and one from Shane Drahm.
And they are clearly in desperate trouble as they struggle to find any sort of form at the start of a run-in which includes games against Leicester and Gloucester before they tackle Harlequins, Bath and Newcastle and a last-day humdinger at Worcester.
Drahm and Van Gisbergen traded penalties in the first 10 minutes, but after that Northampton were comprehensively out-scrummaged and hustled into a series of errors all over the pitch.
Josh Lewsey had already gone close before Bruce Reihana's error – touching down a long kick before it crossed the dead-ball line – gifted a five metre scrum to Wasps in the 19th minute.
Lawrence Dallaglio's drive was stopped short, but Dawson nipped through a gap under the posts to score against his former club with Van Gisbergen converting.
Voyce then struck twice in six minutes to put Wasps in the clear by the half-hour mark, again from two Northampton errors.
Van Gisbergen cruised through a huge blindside hole to put Voyce in the clear from 20 metres out for the first.
Then former England hooker Phil Greening intercepted a floated Johnny Howard pass on his own 10 metre line and cantered clear before putting the wing away again.
Northampton coach Budge Pountney's response was immediate as he replaced both Howard and Drahm before the interval, giving Fulton his debut and Grayson a chance to control the territory from fly-half.
Grayson briefly settled their nerves with a penalty either side of the interval and tried to find the corners.
But normal service was resumed after 54 minutes when Dallaglio's low-level catch and assist put Van Gisbergen into the corner and the full-back converted from wide on the right.
Wasps suffered a casualty in the move, though, with O'Connor helped off the field after damaging his left ankle at a midfield pile-up to put his participation against England next weekend in doubt.
It did not affect the outcome, however, and his side would have scored more points but for some wasteful finishing from Van Gisbergen, who was held up on the line when an early pass would have given former London Irish wing Paul Sackey a try on his debut.
Voyce made no mistake, though, when Van Gisbergen picked off a John Rudd pass and released him in injury time for a weaving 60 metre run to the line at the death.
And six minutes of injury time give Van Gisbergen another chance on the left and he took it with aplomb by breaking a tackle to burst over in the corner.
For London Wasps:Tries: Voyce 3, Van Gisbergen 2, DawsonCons: Van Gisbergen 2Pen: Van Gisbergen
For Northampton Saints:Pens: Grayson 2, Drahm