pulling to one side when braking

[HKstang]

When I get on my brakes whether its really lightly or really hard, my steering wheel wants to pull to the left. If I hold the wheel lightly when coming to a stop and let go just as I let go of the brakes the steering wheel will turn slightly back to the right.

I just had an alignment done, it was doing this before the alignment too. My mechanic said there was a little play in my steering rack, would this be the reason?

Thanks,
Geoff