Steve Diamond gave credit to London Irish's departing star James O'Connor for being the key influence behind Sale's loss.
O'Connor played his final game for the Exiles in the 22-20 win and set up Andrew Fenby's early try.
"He was on fire every time he touched the ball and was the difference between the two sides," said Diamond.
Diamond added that it was difficult to motivate his squad with the playoffs out of reach but European qualification already finalised.
"We want to win every game and, being 10 points up with wind advantage in the second half, we should have done so," added Diamond.
"We should have kicked the points on offer and it would have been nice to finish with a win.
"It was difficult to motivate us for this game when we have already qualified for Europe."
For Irish there was a sense of frustration at not kicking on earlier in the season - finishing 10th overall.
"We found a way to win but our performance was ropey and scratchy," said Smith.
"We could have made it more comfortable than it was had we kicked our goals and not missed our line kicks.
"It's disappointing to finish only 10th, we had an opportunity to kick on and challenge for Europe when we won away at Saracens and Wasps, but we failed to do so. However, we have a relatively strong squad which tested our resources."