[Phil]

Ok, this occurred at teams, but pretend its matchpoints for a moment.

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Partner leads the ♠J. Plan your defense.

[rhm]

I can construct layouts where not going in with the ♠A at trick one costs 2 tricks
West holds: ♠Kx,♥Axx,♦AKQxx,♣Jxx
If you go in with ♠A and switch to clubs declarer is down.
If you duck declarer makes an overtrick.
Nevertheless I doubt that playing the ♠A at trick one is the correct matchpoint play.
Often declarer gets a second spade trick that way.
Most of the time when you loose your spade ace by ducking the trick comes back

Rainer Herrmann

[Phil]

LHO had a similar hand to the one you describe: Kx ATxx AKxx Qxx. I ducked the spade, which is what most warm-blooded mammals would do. Declarer (Jillybean) nicely proceeded to play two hearts and three diamonds. Partner won, and endplayed me with a spade ( ).

Regardless of my partner's defense or level of interest / attention, on this layout I can simply play ♠A, ♠ and let things run their course.

[Fluffy]

unblock ♦J, this can wakeup partner that there is an endplay problem

[PhilKing]

If partner had not endplayed you, you don't get a spade trick. On a club switch, declarer just rises ace, crosses with a heart and cashes the long diamond.