All year long, I've been playing this guy at short:

JoseCueto

He meets or exceed all the recs at short, but is weak w/ the stick.  His .620ish OPS last season was about what I'd expect from him but his .530ish OPS this season (547) at bats is beyond terrible.  He's about the 10th best SS defensively if you go by stats, 18 + plays, 0 - plays, 23 errors.  Overall, our offense has been solid, 2nd in the NL, so he's not killing the overall offense, but we could improve it.

In CF, we've got GordonFoster

He's obviously lacking in range & glove for a CF, but I was hoping he could make up for a bit w/ his arm.  Ideally he'd be a 3rd baseman, but he was our best option this year at CF.  Solid lead off man, lead the league in average w/ a respectable 78% steal rate (31 steals in 40 attempts) and a little pop (20 homers).

For the playoffs, w/ Cueto struggling so much in CF, would it be worth putting Foster at SS?  How much would his defense kill us?  Its not that far below recs?

I've got a top draft pick from 2 seasons ago (CamLong) that projected to be a great defensive CF w/ a really solid stick.  His glove hasn't developed like I hoped (only 2 seasons of development in, so hopefully a new FI next year will kick it up a bit), but he could certainly man 2nd now, hopefully CF next year, w/ my current 2b moving to CF.

Thoughts?

I dont think a 70 glove for a 2b will suffice.  Especially if you have a lot of groundball pitchers... Long's 78/70 at 2B may not cut it.  Lots of stuff up the middle could be in question.

First - with respect to playoffs no one can give you a definitive answer - due to small sample size, it is a crapshoot. Having said that, in a 5/7 game series, by reducing defense, you might get an extra error or two, which might allow an extra run or two, which might be enough to lose a game, which might matter in a best of 5/7.

In your case, I'd be very comfortable moving Foster to SS.

I would also be very comfortable playing Cam Long over a full season at 2B. The question really depends on analyzing player pairs. For example, let's say you decide Long's glove isn't good enough for 2B, where do you put him? LF? If that's the case, look at Cam and LF total offensive production and defensive liability and compare that to Cam and 2B alternative the same way. I suspect you'll net more with Cam at 2B than in LF.