Thought Carl Crawford was expensive? Consider the alternative – something that led the Angels to one of the more shocking moves in recent memory.

Los Angeles (of Anaheim) was interested in Crawford but was left empty-handed after the Red Sox reeled him in on a seven-year, $142 million deal. Jayson Werth, the other elite free agent outfielder in this year’s class, was already off the board by the time Crawford agreed to terms with the Sox. Once those two players were gone, the fallback options were scant.

Magglio Ordonez loomed as something of a consolation prize, and Josh Willingham and David DeJesus represented relatively low-cost options who moved in trades. But all of those players were gone by the middle of December as well.

The rest of the outfield options on the market offered little appeal. Yet the resolution of the Angels’ search for an outfielder was nothing short of stunning.

The Halos made a move on Friday to acquire Vernon Wells in exchange for catcher/first baseman Mike Napoli and outfielder Juan Rivera. On the one hand, Wells is coming off his best season since 2006. He hit .273 with a .331 OBP, .515 slugging mark, .847 OPS and 31 homers, earning his third career berth on an All-Star team.

Almost all of his damage, however, came in the hitters’ haven of the Rogers Centre, where he had an OPS of .991 last year. On the road, he had 11 homers and a .708 OPS.

Moreover, his contract is about to become very expensive, as the Angels will pay Wells $86 million over the next four years, an average annual value of $21.5 per season. Considering that Wells will playing at ages 32-35, the Angels’ willingness to take on what was widely viewed as one of the worst contracts in the majors is little short of stunning.

Put it another way: The Angels were unwilling to pay Carl Crawford $20.3 million per year from ages 29-35 (or, at the least, even though there were some indications that the Angels might have made such an offer shortly after the Sox did so, their owner Arte Moreno griped that the Crawford deal was “crazy”). But they were willing to give a larger annual deal to a player who will be able to offer three fewer years of his prime.

In fairness, the Angels likely view their shedding of Napoli (who, as an arbitration-elgibile player, will earn between $5.3 million and $6.1 million) and Rivera ($5.25 million) as the shedding of about $11 million. Still, even if one views the Angels as “merely” paying Wells $75 million over four years – a somewhat misleading figure since they could have just non-tendered Napoli if they were so eager to avoid paying him – they’re still paying the outfielder roughly $18.75 million a year for the next four years.

There was a time when Wells was a power threat who also featured excellent defense in center. But his defensive range has diminished to the point where the Angels will consider him to play left rather than center, and he certainly doesn’t have the baserunning or defensive impact of Crawford. For that matter, while he did post better power numbers than Crawford last year, he had a worse on-base percentage.

In theory, given two players of comparable skill sets, a team would prefer to acquire a player for a shorter term in order to minimize risk and maximize financial flexibility. That said, in this instance, the Angels appear to be acquiring the player for the wrong part of the term of his deal.

The Sox were willing to give Crawford a premium contract because they would be getting almost all of his career peak, starting with his age 29 campaign in the coming year. The Angels are acquiring Wells when he is likely at the end of his peak. Put another way: A player’s performance should be more valuable in his age 29-31 seasons than his age 32-35 seasons.

Indeed, the fact that Wells represented the alternative to the Crawford deal reinforces an overlooked point about just how unusual it was that the Sox were able to sign an elite outfielder in his 20s.

For the second time in four years, the Angels are acquiring a prominent outfielder entering his age 32 season, with Wells joining Torii Hunter. The Nationals inked Werth this winter to a deal that will run from his age 32-38 seasons. The Mets signed Jason Bay to a four-year deal covering his age 31-34 seasons last winter. Matt Holliday’s seven-year, $120 million deal with the Cardinals spans his age 30-36 campaigns.

It is exceedingly rare to acquire outfielders without some kind of flaw, whether age, defensive deficiencies, makeup questions, durability issues, underperformance … something. In order to find the last time a top-tier free-agent outfielder changed teams while still in his 20s, one has to dial back to the 2004-05 offseason, when Carlos Beltran signed a seven-year, $119 million deal with the Mets while getting ready to enter his age 29 campaign.

The reality is that with Crawford and Werth gone, the Angels seemingly tried to make the best of a bad situation that will exist not only this season but that will carry into next offseason.

Part of the Sox’ calculus in acquiring Crawford this offseason was the fact that next year’s class of free agent outfielders is not terribly appealing. The team recognized that sometime between this offseason and next, it would have to address two outfield vacancies – one created by the expiration of J.D. Drew’s contract, the other created by the expiration of Mike Cameron’s contract.

Ryan Kalish is viewed as capable of replacing one of those players by the time the 2012 season starts. But the Sox don’t have a second in-house alternative who is certain to emerge by 2012, so they recognized a need to acquire an outfielder, either this offseason, during next season or next offseason.

And there was simply no one who is remotely in Crawford’s class in terms of talent and age. There might be some impact players who emerge as market alternatives in the next year – for instance, Jose Bautista of the Jays is eligible for free agency next winter when he will be heading into his age 31 season, and players like Willingham and DeJesus will be reaching free agency.

But there won’t be anyone like Crawford who has a well-rounded game and who is at the beginning of his prime. That, in turn, motivated the Sox to address their outfield this winter, rather than waiting until after the 2011 season.

“When we didn’t re-sign [Jason] Bay and chose to put that money towards [John] Lackey, we knew that [left field] was going to be an area that we’d have to address at some point over the next two to three offseasons,” Red Sox assistant GM Ben Cherington said recently. “We felt like this was the time to do it. As we looked forward, we didn’t find that the likely alternatives next year in the offseason or in future offseasons were as appealing as Crawford given his overall skill set.”

In a way, the Angels’ trade for Wells further reinforces that notion. The landscape for outfielders offered little promise once Crawford signed with the Sox. And so the Angels were left to acquire a player in Wells who will be more expensive (in terms of average annual value, though not total dollars) than him and older.

Perhaps Wells will be sparked by his change of venue, and perhaps he will be able to carry his age 31 bounceback performance forward for the duration of his contract. If that happens, then perhaps the skepticism about his acquisition by the Angels will dissipate.

However, for now, this looks like another example of the Angels acquiring an outfielder at a time when his skills are on the verge of decline, just as they did with Hunter and just as they did with Gary Matthews Jr.

The Red Sox may face a similar reality with Crawford by the back end of his contract (though the club remains optimistic that he will follow the pattern of speedy players who age gracefully). But in the short-term, they will capture some of the best seasons of a player who will impact the game in a number of ways that Wells – and, for that matter, few other players in the game – can match.

“To add a dynamic player like this who impacts the game in every possible way you can, entering his prime,” Sox GM Theo Epstein said on the day Crawford was introduced as a Red Sox, “he’s a game-changer for us.”