It’s beyond evident the Seattle Mariners are trying to win in 2015. That’s the only reason you’d commit $58 million to a guy like Nelson Cruz, and even after that acquisition, the Mariners continue to look to add another bat. If they find one, it’s probably going to be an outfielder, and as the Mariners explore the trade market, some names keep popping up. Names of people to be traded for, but also names of people to be traded away. It seems unlikely the Mariners will elect to move James Paxton. Yet there’s also Taijuan Walker, whose inclusion in a trade could open a lot of doors. Walker might be best described as not unavailable, so it’s worth thinking about how much value he might possess at the moment.

There’s obviously a lot to like. Walker’s young, and a year ago, he was ranked by Baseball America as the No. 11 prospect in the game. As a starter in the bigs in 2014, over limited time, Walker showed his usual great velocity, averaging a fastball almost as fast as Stephen Strasburg’s. Walker was sidelined by a shoulder issue, but he recovered and resumed pitching, so that seems like a thing of the past. Those who evaluate young players by their ceilings see in Walker a potential future ace. That’s also not a great way to evaluate young players.

Here’s a simple starting point for the Walker skeptic’s argument. Over 29 starts in 2015, Steamer projects Walker to be worth 1.2 WAR. And while we’re somewhat accustomed to seeing young players have their ups and downs upon establishing themselves in the majors, pitchers don’t follow the aging curve you believe that hitters do. Pitchers don’t build up to a late-20s peak. At least, not on average, since they tend to start losing velocity young. Looking at Walker more specifically, the fastball’s good, but it has limited support. His offspeed pitch is a work in progress, which is true for every starter who doesn’t yet have a good offspeed pitch. Evaluators like Walker’s curve less than they did a year or two ago, and it’s unclear what Walker intends to do with his cutter. In the upper levels, Walker has yet to post a good strike rate, or a great whiff rate. So it’s not all rosy. Walker very much remains a prospect.

A good one. One who could contribute right away. If Walker were hypothetically a free agent, he’d be in great demand. But where’s his trade value? I can’t answer that specifically, but we can look for some comps. Walker is a year removed from being BA’s No. 11 prospect. Since then, his value has gone down, but it hasn’t by any means cratered. I went over the last five years of BA top-100 lists. I identified pitchers who were traded either as top-25 prospects, or a year after being top-25 prospects. A table of information is below, and it happens to include Walker himself, since he was almost traded a couple years back. There was reportedly an agreement, and it was just blown up by a no-trade clause. But there’s no sense in throwing away the information.

Let’s add some detail, proceeding in order. Skaggs is an interesting comp for Walker. A year after being ranked No. 12, Skaggs was packaged with Adam Eaton to bring in three years of Mark Trumbo. Skaggs’ value dropped some in 2013, similar to Walker, and he brought back an average young player with one notable skill. Yet Skaggs was also sent with a pretty steady and average-looking center fielder in Eaton, so it’s not like Skaggs got Trumbo straight-up.

Bauer was dealt by the same team as Skaggs. Though there were other parts moving around, you can basically look at it as Bauer for Gregorius, from Arizona’s perspective. They had their issues with Bauer, organizationally, and Gregorius is a big-league shortstop, but at the time, Bauer was BA’s No. 14 prospect, and Gregorius was No. 80. That hints at the value of a pitching prospect, relative to the value of a position-player prospect.

Turner’s different, in that that was a midseason trade. But still, it counts, and Turner was packaged with a decent catching prospect to bring in a few months of Sanchez and a year and a few months of Infante. Turner was ranked as a solid prospect three years in a row, but his value dropped in 2012 before getting dealt.

Montgomery is a forgotten component of the Shields/Myers trade. It wasn’t Montgomery who brought back Shields and Davis; it was Wil Myers who did that, plus secondary pieces. Myers was a top-5 prospect, Jake Odorizzi was a top-100 prospect, and Montgomery was a prospect with diminished value. In 2012, Montgomery ran an ERA in the low 6’s. Walker’s more valuable than this.

Pineda, in a way, is the opposite of Montgomery. Pineda entered 2011 as the No. 16 prospect. Then he struck out a batter an inning over 28 starts in the majors. He got dealt for the No. 6 prospect, who had also previously been the No. 3 prospect and the No. 4 prospect. So Pineda’s value skyrocketed after being ranked, making him roughly equivalent to a top-of-the-line position-player prospect. Walker doesn’t have this value.

Going back further, Kelly was the centerpiece of Boston’s trade for Adrian Gonzalez. A year after being the No. 24 prospect, Kelly slotted in at No. 31, and he was also packaged with Anthony Rizzo, who was ranked No. 75. Technically, it was a trade for Gonzalez before his contract year, although the Red Sox signed Gonzalez to a more or less market-rate contract extension shortly thereafter. So Kelly and Rizzo fetched a whole lot of years of Gonzalez, but in all but one of those years, Gonzalez was to earn fair wages.

The oldest trade here includes Drabek fetching Roy Halladay before his own contract year. Like Gonzalez, Halladay signed a contract extension basically as a part of the move. Unlike Gonzalez, Halladay signed for a below-market deal, agreeing to three years and $60 million as arguably the best starter in the sport. Maybe not even arguably. Drabek at the time was the No. 25 prospect. He was moved along with the No. 29 prospect in Michael Taylor, and the No. 81 prospect in Travis d’Arnaud. So Drabek and Taylor were sort of co-headliners.

Because the Walker trade didn’t happen, we don’t know all the official details, but based on reports, it was going to be three years of Upton for Walker, Nick Franklin, and two other lesser pieces, maybe out of the big-league bullpen. Walker at that time was BA’s No. 18 prospect. Franklin was No. 79. Walker now is closer to the majors than he was then. However, he still has a lot of the same question marks, despite two more years of development.

As one last throw-in, because it shouldn’t be ignored, the Cardinals did recently trade Shelby Miller and a prospect for one year of Jason Heyward and a useful reliever. For simplicity, let’s break it up, as Miller for Heyward and prospect for a reliever. Miller’s two years removed from being the No. 6 overall prospect. He was pretty good in 2013, then he took a step back in 2014. So while Miller has four years left of control, while Walker has six, Miller’s also more established in the majors. He got one year of a great player.

Miller’s an interesting if exaggerated example of the reality of pitching aging curves. After posting a 99 FIP- as a decent Rookie of the Year candidate at 22, Miller at 23 saw his FIP- rise to 125, as his strikeouts went down and his walks went up. So Miller now is by no means a shoo-in as a worthwhile starter in the season ahead, despite his encouraging background. You see a young age and you want to believe in the potential, and while it’s better to be young and talented than old and talented, pitchers aren’t simple to track, and of course they’re also just less reliable than their position-player equivalents.

So, Taijuan Walker? There’s value there. Less than there was a year ago, but he’s still a big-league starter with six more affordable years. For additional reference, maybe we can consider the usual prospect-valuation links. Walker was the No. 11 prospect. He won’t show up on prospect lists anymore, but where might we put him now? Still in the top 50. Somewhere between 20 – 50, let’s say. Ballparking it, we’d be looking at a surplus-value total in the vicinity of $15 – 30 million. $30 million, if you love Walker’s fastball and believe he’ll grow more accustomed to his recently-tweaked mechanics. $15 million, if you acknowledge the youth but wonder about the secondary stuff. Walker’s market value will vary by team, as different teams have different evaluations of young players.

Most commonly, of late, Walker has been linked to Justin Upton, again. Upton has one year left to go. Steamer sees 3.1 WAR, and Upton will earn 14.5 million. If you figure the market’s paying $7 million or so for a win, Upton would have $7 million in surplus value, roughly. If you go with Dave’s latest estimate of $7.5 million or so for a win, Upton inches closer to $9 million. And then if Upton were to have the season he had in 2014, he’d show up at $15 million just about on the nose.

(Update: and as I initially neglected to remember and include, Upton will probably be good enough to warrant a qualifying offer after the year. So then there’s additional value in receiving a compensatory draft pick, assuming that Upton would not be re-signed. How such picks are valued isn’t precisely nailed down, but it stands to reason these picks are worth a few million dollars.)

All this surplus-value stuff is just estimation, and that’s why I included the table of recent trades as well. Straight up, Taijuan Walker for Justin Upton would seemingly favor the Braves, but it wouldn’t be completely lopsided. You can actually make a convincing argument that Upton and Walker offer similar value. Now, it seems like Walker is more valuable, but probably not by a landslide. But that at least establishes a general idea. Walker, by himself, could fetch a pretty great player on one year, or an average or good player on two or three years. Alternatively, Walker could be exchanged for a lower-ranking position-player prospect, although that wouldn’t do anything for the 2015 Mariners. If Walker were packaged with more pieces, then, naturally, the return would improve.

Adding to the complexity is that Walker is a part of the Mariners’ projected starting rotation, and they have very little organizational depth, and with the payroll approaching its ceiling there’s a lot of immediate value in slotting in Walker for the league minimum. Walker would need to be replaced; that replacement would cost the Mariners money. That’s among the reasons Walker probably will not be traded. But he is available, for the right price, and based on estimates and on the history, that right price isn’t extraordinary. At the end of the day, Taijuan Walker’s a pitching prospect with question marks.