OK, the rumor is that Wren's willing to listen on "anyone" if the deal makes the team better, including Martin. Are there replacements or potentially better potential LF bats available than Prado? Arguably, yes. The much more important question facing the organization is whether the increase in available funds Frank Wren has alluded to is enough to pay for enough of an everyday LF upgrade over Prado if he's traded to offset the versatility he provides.
On the surface, Martin is "irreplaceable". The question I have is, is he really? The widely accepted theory is that either Martin or Dan Uggla are the eventual "replacement" for Chipper Jones when he walks away (with the other one manning 2B). However, I can't recall a time that I've seen any of the higher-ups in the organization take that stance. They asked Martin to switch positions when Uggla was acquired because he's the more athletic of the two. You'll get no argument from me that that was logical - regardless of the metrics, the perception is that Prado is an average (to a notch above) defender in LF, Chipper is below-average at 3B, and Uggla is below-average at 2B. While that's not ideal, Martin typically spent his time in winter ball in LF, making him much better-suited to play there rather than exposing Chipper to even more potential time on the shelf with a shift back out there (an experiment that already proved disastrous once before). While fans and some writers pined for Uggla to be the one moved, asking that much of him in one offseason (shortened by trade) simply doesn't seem to be something that would have been beneficial at all.
Martin's perceived value to the Braves is his versatility - that not only is he capable of handling the move to the outfield, but that he provides the organization a player capable of stepping in for not only Chipper at 3B for extended periods, but for Uggla at 2B and even Freeman at 1B. The Braves consistently "got by" without production from the spots most teams typically have big bats because they often got it from places those teams didn't - 40+ HRs from your CF (Andruw Jones) tends to hide the fact that your 1B isn't hitting 30 bombs. Of course that was at a time when Chipper was a "given" to net you .300/30 HR/100 RBI.
In my opinion, the reason Wren is looking for an "upgrade" is because the team simply can not take that next step without that one more "big bat", even if it costs you a little flexibility to find a place for it in the lineup. Uggla offers big bat production from a position you don't historically get it from, which is always helpful. The problem is that even with him, the Braves have a lineup with "solid" hitters, but the only one capable of putting the team on his back for any extended period was Uggla. This isn't meant to be a knock on anyone in particular - it's not that several of these guys aren't capable of developing into that type of hitter, just that they weren't in 2011. The point is this...Chipper can be the Chipper of old that scares everyone to death for stretches, but those stretches are much shorter and further apart than several years ago. It's unfair to expect Brian McCann to be the guy to carry your offense when he's catching 5-6 times a week. You had typical "glove guy" production at SS. While CF received a huge upgrade with the acquisition of Michael Bourn, it's not the "instant offense" that the team has always thrived on (station-to-station, 3-run homer offense - the old Earl Weaver and Bobby Cox staple), meaning they had to adjust to take advantage of what he provides. Of course, the player most affected by Bourn was Prado - generally an aggressive hitter early in the count when he gets something he feels he can handle, Martin was asked to keep that in check at times to allow Bourn the opportunity to run.
The general consensus (that I share) is that the Braves have more than enough pitching to be legitimate World Championship contenders if they can just get consistent offensive production rather than having to rely on the same guys to produce night in and night out. The wild card the organization counted on that doomed the 2011 campaign was the regression of Jason Heyward. The team got just about what they expected everywhere other than RF, even with Uggla's early slump, McCann's late slump, and Chipper's expected downtime. Freddie Freeman met or exceeded just about every realistic expectation during his rookie season, much like Heyward in 2010. He's going to face the same challenges Jason faced going forward - now that the league has seen you several times, the "book" on him is much more detailed and Pitching Coaches and advance scouts have months to review video with their staffs to make them understand that there are simply places you can't go when facing him. Both guys have proved both smart enough and talented enough in the past to make their adjustments after the Pitchers change their approach. However, it's a process that historically takes time, and often more time with younger players at this level. Again not a criticism of either player, just a statement to point out that while both guys' rookie campaigns were exceptional and good enough to make them very nice bit players for any contender, they're not the player other Managers decide before the game they're not going to let be the guy that beats them.
Chipper used to be that kind of player. Dan Uggla is that type of player. Heyward and Freeman may turn into that type of player in the future. As much as Braves fans love Martin Prado's team-first attitude and gritty play, he's never going to be that type of player. So the argument becomes, is the team stronger with a gritty guy making $4.5 million that can play all over than it is if it can clear that money to pursue either a prototypical power bat for LF or offensive production at a non-typical position like SS? Wren has stated publicly that payroll will increase this season (even though it's been all but impossible for anyone not in the room when he and the bean-counters number-crunch to figure out what spending COULD occur). The Derek Lowe trade cleared at least $5 million. Prado's projected arbitration raise will be to around $4.4 million. Jair Jurrjens is also widely rumored to be "available", and his projected arbitration raise will be to around $5.1 million. Assuming Prado and JJ are both moved this offseason and the projected payroll increase is enough to cover expected raises and renewals, that would give Wren roughly $14.5 million to address LF or SS if he wanted to pursue a big-name type of player even if the return for Prado and JJ was only prospects and salary-relief.
When $8-$10 million could get you a Jimmy Rollins to play SS and hit behind Michael Bourn (to become a team much more capable of playing "small ball") or a Josh Willingham to play LF and hit between Freeman and Heyward, Martin Prado is absolutely available, just as he should be. A lineup with either of those guys in it should be deeper and more consistently productive without having to unfairly ask Heyward and Freeman to become superstars before they're ready to take that step. Tyler Pastornicky profiles much more like the type of 2-hole hitter you'd prefer to have behind Bourn than Prado does, and adding a 30 HR bat would make the lineup much more dangerous.