Sean O'Brien has been dealt a blow in his bid to make Ireland's final game of the Six Nations next weekend.
The flanker was making his comeback from a hip injury in Leinster's refixed Pro 14 clash with Scarlets this evening.
However, he lasted just 27 minutes, before being forced off the field with a shoulder problem.
Schmidt had hoped to have the 31-year-old back in contention for his team's potential Grand Slam decider with England, but the flanker's participation in that Twickenham clash is now unlikely.
Fly-half Dan Jones kicked a last gasp penalty to secure Scarlets a dramatic 10-10 draw against PRO14 Conference B leaders Leinster at a rain-drenched Parc y Scarlets.
Scarlets were trailing 10-7 and just as the clock went red referee Nigel Owens awarded the home side the key penalty.
From 28 metres Jones put the kick through the posts. The draw keeps Scarlets three points behind Leinster in Conference B.
After a scoreless first half, Leinster thought they had done enough after the break with a try for hooker Ed Byrne and five points from the boot of fly-half Ross Byrne. The Scarlets scored with a try for centre Paul Asquith converted by Jones.
In the rain and wind, Scarlets were on the defensive from the opening whistle. Full-back Dave Kearney ran back a poor clearance from Jonathan Evans and Leinster set up camp in the home 22.
It needed a brilliant turnover from Tadhg Beirne, who is Munster-bound at the end of the season, to help the Scarlets clear their lines but they continued to struggle to get out of their half.
Scarlets did well to keep a clean sheet in the first quarter helped that hooker Bryan Byrne knocked on just as Leinster had a sniff of the try line.
Leinster suffered a blow when captain Sean O'Brien, in his first game since December, had to leave the field on 27 minutes with an arm injury.
And two minutes later Scarlets looked like they had made the most of their first visit to the Leinster 22 with Tom Williams stepping inside from the right to go over, but TMO Neil Hennessey stepped in to disallow it for a loss of control in the act of grounding.
In the end the first half ended scoreless, but it took only four minutes of the second to break the deadlock with hooker Byrne getting over after the Irish team had made the most of a scrum inside the Scarlets 22. Ross Byrne converted.
The Scarlets responded positively and went through 19 phases inside the Leinster 22 until scrum-half Jonathan Evans knocked on.
But Scarlets came again with a driving maul. Beirne broke away before Asquith finished well. Evans converted to level the scores at 7-7 on 66 minutes.
Leinster's loss of the lead only lasted six minutes however as Ross Byrne put over a penalty kick after Scarlets were caught off their feet at a ruck.
Leinster thought they had extended their lead on 75 minutes but Nick McCarthy's try, following a charge down, was ruled out by the TMO for offside.
If that was not dramatic enough a try was ruled out for Scarlets' new signing wing Tom Varndell before Jones' penalty right at the death.