O'Brien set to feature for Ireland
The 27-year-old flanker is primed to end 14 months of injury woes by featuring for the Irish Wolfhounds against England Saxons on Friday night.
O'Brien has endured two bouts of surgery on the same shoulder since his last Test action, in Ireland's 24-22 New Zealand defeat in November 2013.
The bullish British and Irish Lion could now make his long-awaited full Test return in either Ireland's second-round clash with France or their March 1 showdown with England.
"Sean trained fully on Tuesday to be honest," said head coach Schmidt, as Ireland prepare to open their campaign in Italy on February 7.
"So we'd be hopeful that he'd be involved in the first half of the Six Nations."
O'Brien's club Leinster believe the combative loose forward could feature in Pro12 action against Newport Gwent Dragons on February 15.
Ireland host France in Dublin on Saturday, February 14, so if O'Brien is embroiled in club action that weekend, his Test return would then come against England.
Schmidt's Ireland side entertain England in Dublin when this year's Six Nations reaches its midway point, and O'Brien's return would prove a tangible mid-tournament boost.
Loosehead prop Cian Healy has been battling hamstring problems since September, and is another aiming to return to the Test arena during the upcoming competition.
Schmidt still believes Healy will feature during the tournament, but sounded a note of caution in respect of the destructive ball-carrying front-rower.
Schmidt vowed not to take any risks with his crop of stars working their way back to fitness, especially in World Cup year.
"We're still hopeful that Cian may have an involvement as well," said Schmidt.
"Cian looks in great shape; he's just got to hit a few markers to finish off his full recovery.
"Because one thing we don't want to do is to have someone reinjure themselves and therefore put themselves out for an extended period of time.
"So we're very much Six Nations-focused but it's a massive year, and what we can't afford to do is worsen a situation for a player with an injury."
Schmidt moved to allay fears surrounding the severity of scrum-half Conor Murray's neck problem, tipping the Munster half-back to recover in time to face the Italians.
Murray has disc trouble in his neck, but Schmidt believes this has been caused by bruising and swelling: if both subside in time, the British Lions playmaker should be ready to start the tournament.
"Conor is feeling really good, we're quietly confident," said Schmidt.
"He's got a few more things to tick off and he will be scanned again by the end of the week.
"And by Monday we'd like to have a clear picture so we can have uninterrupted preparation for Italy, but at the moment we're hopeful he'll be okay.
"If you get bruising, bruising causes swelling, and swelling causes discomfort.
"That's a layman's view of what Conor has got presently, so we're hopeful that will dissipate, and has dissipated over a period of time since it first happened."