How can you say he didn't leave the baseline? Does the baseline extend all the way into the outfield? He was past the base and the next base is a totally different direction than where he was going. While I get the whole direction going into the base is the established line to determine if someone is avoiding a tag that does not fall under this. He's no longer in the basepath because he's no longer attempting to go to a base.
I think the slide that took out Kang was a good one. It falls within the rules of Coughlan can reach the base and Kang has a chance to protect himself. If I remember correctly this was another situation where it was a slow developing play and Kang shouldn't have tried to continue on to first. If the fielder is beside the base then the runner should be able to slide past as long as they are touching the base. If that happens the fielder has the chance to see what's happening and make a decision to protect themselves or try to continue. If the fielder is behind the base then you are targeting the fielder.
Going from memory, but I believe that Kang actually completed the double-play on that one.
I thought this article, discussing players' reactions, was interesting: www.foxsports.com/mlb/just-a-b...players-speak-101115
Especially this quote from a player:
"Watching this play scared me for reasons different than one might expect. With the season on the line, and a 2-1 score the tying run was on third base. If I were Chase, I would have gone through my mental checklist. Half way on a fly ball, but tag if I thought I could divert the OFer's attention away from the man on 3rd. Don't let my self get tagged by the second baseman on a grounder hit to him. Make sure to freeze on a line drive and not get doubled off. And most importantly on a ground ball make sure to do EVERYTHING in my power to break up the double play. I don't know how late I would have slid, or exactly how I would have reacted once I reached the base, but I would have been willing to sacrifice MYSELF physically to make sure to prevent that double play. I believe Chase was thinking the same way. He was not intending to hurt Tejada, he was willing to hurt himself. I place no blame on Chase for his actions and all the blame on the rules surrounding the play. The umpires have never used their discretion to accurately enforce the rule, allowing slides like this to happen. Chase wasn't thinking about Tejada, or his own safety, he was thinking about his team. Watching the play scares because I believe I would have done the same thing and perhaps caused the same injury to Tejada, or one to myself."