[greymule]

Interesting, but as long as there was a chance for a play somewhere, I think I'd have gone the other way. The book says, "interferes with a fielder attempting to field a fair batted ball." It doesn't add, "unless the runner is legally sliding in an attempt to reach a base" or "unless the runner would have been safe anyway" or "unless the interference is utterly unintentional." A few years ago, I had a similar play (though not a force) in a slow pitch tourney:

R1 on 2B, 2 out. B1 hits medium pop to F5, who stands about a foot inside 3B, in the baseline, to catch it. Just before the ball reaches F5, R1 executes a legal slide and contacts F5, knocking him off balance but not down. I called interference, 3 outs. The runner has to avoid the fielder, whether the runner is doing everything "right" or not.

You could ask, "What option did the runner have?" but sometimes there is no good option. It's just a bad break.

I admit I would have a no call in this case: R1 on 1B. B1 hits roller that goes past F1 and toward 2B. R1 slides in safe at 2B and gets tangled with F4 well before the ball gets to 2B. I determine that F4 had no play on B1.

I doubt if the ASA case book gives a play like this, but I'll check it now.