Upton is a no doubter. Utley and Tulo are two of the elite at their position, so those are keepers.
It's tough to give back Teixeira, but 1B is incredibly deep this year. Ditto Zimmerman.
I think Sizemore and Felix are your next two options. Sizemore has been a perrenial first rounder, and while Teixeira will surely get drafted ahead of Felix in a re-draft league, Felix is 6 years younger and provides more value in a keeper league.
First of all, if the rules don't change, you have correctly identified your top-7 options: Teixeira, Utley, Halladay, Sizemore, Hernandez, Tulowitzki, and Justin Upton. And you definitely need to keep 5 of them. Not only are they all worthy of a pick in the 1st 5 rounds, they will all probably go in the top 3 or 4 rounds this year.
With only 5 keepers, I think you can only hold onto 1 SP...especially with the quality of your hitters. Take your pick between Felix and Halladay...they are both top-5 SP's and roughly equal in value. Keep whichever guy you like the most. You can't go wrong either way.
With the hitters, you must keep Teixeira and Utley. I think you also need to keep the young kid, Upton. That leaves a choice between Tulo and Granderson. Considering Granderson's down year, and the fact the Tulo plays a scarce position, I would keep Tulowitzki. I think it will be a lot easier to find a solid OF in the draft than a SS. But again, you really can't go wrong.
Now, if the rules change: Again, I think you are on the right track with Utley (Rd 1), Teixeira (Rd 2), Hernandez (Rd 8), Tulowitzki (Rd 22) and Justin Upton (Rd 23). You don't tell us what rounds Halladay and Sizemore went, but you are getting good (or at least fair) value in all of your options....and my guess is Halladay would cost you much higher than an Felix'a 8th round pick, and that Sizemore wont quite give you good value based on his down year in '09.
There is one more guy to consider, though, if the rules change...and that's Curtis Granderson. Now that he is being traded to the Yankees, his value jumps. And depending on what round he was drafted, he just might be a better value than Teixeira (rd.2). You are basically getting Teixeira at full price in that spot (and there is nothing wrong with that for a player of his talent). But 1B is a deep position. So if you could keep Granderson (and your 2nd rounf pick) for a bargain draft pick, he just might be a better option than Tex. If Granderson is a 10th round or later, I would strongly consider him. (All this is assuming that, as defending champ, you will get the last piuck in the 1st round and first pick in the 2nd round of the draft).
Thanks man, that was more in-depth than I expected. The rules did change, so we're going by round (I think I was botp'd on page 1, so that was buried).
Halladay and Sizemore were kept last year, so if I were to try to keep them, they'd cost me first-round picks (or presumably 3rd and 4th after Utley first and Teixeira second.) Granderson was kept by someone last season, but during their late-season push, they ended up dropping him when he was slumping. I picked him up as a FA, which means he'll only cost me a last-round pick.
We're going to learn the draft order in about a week and a half or so (my semester is over, I'm getting those guys together for a card game anyway, so we're going to try to turn it into our "winter meetings" of sorts ) so we're all bringing our trade blocks and seeing if anything gets worked out. But assuming I'm not going to make a trade, since I won the league last year, odds are that I'll have the last pick in round 1 (and since it's a snake draft, the first pick in round 2.) If that's the case, I only have to worry about keeping one of Tex/Utley, because I can just redraft them with my second round pick. And if I can assume everyone else is going to keep at least one player that they kept last year, that means everyone's first-round pick is going to be a keeper, and I wouldn't have to keep either of them (BIG gamble if I decide to go that route) and just redraft them in the first and second round. If I do that, I figure I'm looking at Felix in round 8, and Granderson, Tulowitzki, Sandoval and Justin Upton 20-23, which is a ton of value, but I don't know if I have the, um, testicular fortitude to try to do that.
But that's all just speculation, and I need to know my draft position before I worry about all that. But boy, am I hoping I get stuck at the end of the round...