I just read a review on the Sigma 70-200 f/2.8 and didn't see that it had VR? Is this true and if so is that an issue with regards to motion? Where would you suggest I purchase this lens?
VR isn't really that useful for sports, so no VR is no big deal.
I can definitely recommend that Sigma 70-200 f/2.8 HSM Macro, it's fantastic. I used one (I've stated before in some other thread...) for a bunch of football games and other sports. I never got to shoot lacrosse (I was always playing... I was starting "attack." Good times, wish I had pictures because I had some pretty sick games.), but I'm familiar with the game and can imagine the kind of shots you'd want.
For the most part you'll be focusing on players cradling, shooting, or passing the ball. The ball itself is too small and fast (plus it's white, and most stick heads are white as well) to really concentrate on, so most of your shots you're going to want the player primarily in focus, maybe with the ball leaving the stick on a pass, but it's not like football where I'd get focus on a receiver and you'd see the ball's trajectory from the QB. You could also frame a few, say your team is on offense in 1-4-1, and you're near midfield... you could shoot a shot with the middie at the point (or the attackman at "X") throwing a pass to one of the wingers and have the winger out of focus (but with his stick up ready for the pass) in the background. Or vice versa, the winger with his stick up ready to catch and the playmaker making the pass out of focus in the foreground. On defense you could get the players making checks (maybe a little blur from a slap or wrap check could look good here), and the goalie making saves (probably don't want those blurred).
Critical part of sports: Anticipation. Getting a few shots of players running around is useful sometimes, but for the most part you want players in action, checking or doing something with the ball. A player moving to a new position is interesting but not as a photograph since you have no relation to what's happening outside the frame.
So in this respect, the fast AF and 2.8 aperture of the sigma would be ideal. When I shot football I was using the school's Rebel body (max ISO of 1600), the field was dark as crap, and I still had shutter speeds of 1/200 to 1/250. If your games are in the daytime then that's even better, you can stop down the lens and get a wider DOF, so more players in focus.
Oh and the sigma could also double as a decent portrait lens, if you wanted to do individual player no-helmet shots. Keep your tamron 28-200 though, and use the 28mm to get the whole team into the shot.
Oh and just to be clear since Sigma lens names are complicated, this is the lens I'm referring to:
http://www.keh.com/camera/Nikon-Autofocus-Non-Mfg-Zoom-Lenses/1/sku-NA09999043586K?r=FE
http://www.photozone.de/nikon--nikk...ex-hsm-apo-dg-macro-nikon-review--test-report