Schmidt was particularly disappointed with the performance of Lacey at the scrums where Leinster, who appeared to have the upper hand, were thwarted time and again by the Munster official’s whistle.
Schmidt said: “We are incredibly frustrated. We thought we had the dominant scrum but the referee didn’t see it that way. It reached the stage where even when we were going forward three or more yards, the penalty went the other way.”
However, Leinster also had themselves to blame for letting slip a game they had taken early control of and failed to score a single point after the eighth minute.
Leo Auva’a crossed early on but that was not enough to stop Leinster slipping to sixth in the RaboDirect Pro12 standings as Eli Walker crossed while fly-half Matthew Morgan kicked the rest of his team’s points as the Ospreys claimed a fourth successive win over the Dubliners.
Schmidt said: “Credit to the Ospreys, Morgan kicked well and it was a great break by Richard Fussell for the try and that was the pivotal moment in a see-saw game.
“We are sixth in the league now and I’m pretty uncomfortable with that position. I would have preferred to go into this [autumn] break on a far better note.
“There are now seven or eight teams in the mix for the play-offs and it’s going to be a mad scramble to make it.”
It had looked a different story early on when Issac Boss made up for the loss of Leinster’s international contingent with an intelligent display in wet conditions.
The scrum-half put Leinster on the front foot with a dangerous break virtually from the kick-off, before Madigan then kicked the opening points of the game.
However, it was the boot of Boss that went close to creating the game’s first try.
He was quick to identify an acre of space behind the Ospreys from a lineout and had both the vision and skill to hoist his kick over the top, only for the speed of the ball to skip off the greasy turf and elude a despairing lunge by Fionn Carr with not a black jersey in sight.
Leinster did get the bounce of the ball from the resulting lineout.
Rhys Ruddock got his hands to Rhys Webb’s clearance kick just a yard off the Ospreys try line. The spinning ball eluded Andrew Bishop and Auva’a beat captain Shane Jennings to touch down. Madigan’s conversion opened a handsome 10-0 lead after just eight minutes.
Ruddock again proved he was back to full match sharpness with a try-saving tackle on opposite number George Stowers but Matthew Morgan kicked a brace of penalties to trim the lead to 10-6.
Leinster then missed two chances to extend their advantage.
Again Boss was the catalyst with another smart blindside break that released Conway. The wing’s kick deflected off Fussell but Conway could not re-gather in time.
A sustained period of pressure earned a penalty but Madigan steered his effort across the face of the posts. That miss felt worse as Morgan struck with the last kick of the half to leave Leinster just a point ahead at the break.
On the back of that success, the Ospreys began the second half the more lively and Walker went close after Conway had failed to deal with Fussell’s kick through.
Both kickers missed with their next efforts, including one from the halfway line by Madigan after veteran Wales prop Duncan Jones was shown a yellow card following a burst in midfield by Auva’a.
With kicking conditions difficult, Madigan threatened to cross the line with an impressive burst that was thwarted by Webb’s fingernails.
Yet with Jones in the sin bin, the Ospreys still produced the game’s defining moment. Morgan took a quick lineout and full-back Fussell glided past Ruddock, Ben Marshall and Thomas Sexton and handed Walker a straight sprint to the line in the 61st minute before Morgan added a late drop goal.
Scorers for Ospreys: Try: Walker. Con: Morgan. Pens: Morgan 3. Drop goal: Morgan.
Scorers for Leinster: Try: L Auva’a. Con: Madigan. Pen: Madigan.
OSPREYS: Fussell, H Dirksen, Isaacs, Bishop, Walker, Morgan, Webb, D Jones, Dwyer, Rees, Peers, J Thomas, Stowers, Lewis, Bearman.
Replacements: Fotuali’i for Webb (58), King for Peers (61), Allen for Bearman (80).
LEINSTER: D Kearney, Conway, Macken, Goodman, Carr, Madigan, Boss, van der Merwe, T Sexton, Hagan, Browne, Toner, Ruddock, Jennings, L Auva’a, Marshall.
Replacements: Tracy for van der Merwe (80), Moore for Hagan (70), Marshall for Browne (26), Murphy for Marshall (65).
Ref: John Lacey (Irl).