This stretch of the season is often the toughest for owners. Most of the big breakouts have already happened (hello, Michael Pineda, Alex Avila and Matt Joyce), plenty of the bounceback candidates have proved they can still play (right, Lance Berkman, David Ortiz and Josh Beckett?) and many of the elite prospects have been called up (thanks, Eric Hosmer, Jordan Lyles and Dustin Ackley). That leaves owners who missed out on those players to seek help either via trade or by identifying — and adding — players who have underperformed so far. This late in the game, it’s a trickier decision-making process because all the options come with some ugly pock marks (hence, the underperforming and all), but there are always a few possibilities for second-half surges. Like these three American League outfielders.

Of course, none of these picks come with a promise or guarantee of a turnaround. But fact is, while they’re all available in the majority of leagues* because they’ve performed below expectations this year for a variety of reasons — not the least of which is injury — they also all have a history of success in the big leagues. That’s the sort of player that an owner sitting in the middle of the pack in a deep mixed league should be targeting to help make a midseason push toward the top.

*Owned in 50% or less of both Yahoo! and ESPN leagues.

Vernon Wells, Angels

Yahoo!: 47% I ESPN: 49.6%

Look, we know the guy gets vilified for not being worth his contract — and rightly so, because he’s not — but that hatred seems to spill over into the fantasy realm when, in reality, it should not. Of course, there’s more to his low ownership totals (which have been creeping upward lately) than just residual backlash over a terrible contract. Like that .205 average. Or the preseason hamstring injury. Or the groin strain that caused him to miss 26 games in May and June. But! Wells is also hitting .250 (17-for-68) with 5 homers in 18 games since his return to the lineup on June 7. And even though many figured the 32-year-old wouldn’t be able to replicate his resurgent 2010 (career-best .242 ISO to go with 78 extra-base hits) — especially after leaving behind the Rogers Centre, which is particularly friendly to right-handed power — it’s also probably no coincidence that Wells’ horrendous start with his new team (.174/.216/.248 through April 30) coincided with the lower-body injuries. I never like to make assumptions (here’s why), but if we can figure that Wells is finally healthy and has his legs under him, there’s reason to be optimistic about a guy who owns a career .194 ISO. In fact, there’s a good chance Wells smacks double-digit homers from here on out. And even though he’s not likely to hit better than .250-.260 going forward, especially with such a poor walk rate (4.1%), his BABIP is a measly .215, and it wouldn’t be entirely foolish to expect at least a little bounce back to his career norm (.285). There’s value here, especially for owners in need of some pop.

Luke Scott, Orioles

Yahoo!: 22% I ESPN: 28.5%

For all the injury issues Wells has had to overcome, the 33-year-old Scott has him beat. On top of suffering from a groin strain in early April, Mr. Birther has been playing through a torn labrum for the past couple months, at least. So yeah, not the most promising rest-of-season prognosis. But then again, that’s why a guy who’s averaged 28 doubles and 25 homers over the past three seasons is even available in three-quarters of leagues. Well, that and his .237 average and .751 OPS this year. But looking at his career with the O’s, he’s put up a BABIP in the .285-.290 range with an accompanying average around .265 — and right now his BABIP sits at a slightly deflated .268, so there’s a little room for improvement there. Plus, his walk (10.5%) and K rates (25.3%) are about in line with his career numbers (11.1% and 23.1%, respectively), so there’s some more hope he can pick up the average. And it’s not like the power is gone: A .196 ISO and 9 homers would look much better if he were hitting .260, especially in 2011’s offensive environment. If you’re going to take the plunge and pick up Scott, you should be further encouraged by his homer off Aroldis Chapman — on a 96 mph fastball. The lefty-hitting Scott, who’s always struggled a bit against southpaws (.242/.319/.473) is batting just .171 with a .231 OBP in 2011. Yet he’s actually slugging .571, and the shot to right-center off Chapman — his fourth against a lefty — might indicate he’s ready to embark upon one of his notorious hot streaks.

Josh Willingham, A’s

Yahoo!: 18% I ESPN: 15.6%

Another injured slugger. Sensing a trend? At the time he was felled by a left Achilles injury, Willingham, 32, was leading the A’s in homers (10) and RBIs (42). Okay, so that’s like saying someone’s the most talented member of the Backstreet Boys.* Still, the left fielder is eligible to return on July 3, and he’s said he thinks he will be able to be back on time. I’m a little more worried about him than the first two on this list, given that he’s hitting just .231 despite a solid .297 BABIP. Also? His 16.8% line drive rate is below average, and he’s making less contact and swinging-and-missing more than he ever has before. But if you’re looking for a positive in all that, his 13.3% HR/FB rate is right in line with his career number, so he’s still managing to muscle balls out of what is one of the toughest stadiums for right-handed batters. Maybe he’s just trying too hard to hit homers, and thus making less contact, which is hurting his average. Or maybe he’s still getting acquainted with the American League after spending his entire career in the Senior Circuit. Whatever the reason, I wouldn’t expect any miracles, but if Willingham’s owner dumped him once he hit the DL, he might be worth an add. Especially if you’re debating between Denard Span and David DeJesus instead. Hey, beggars can’t be choosers.

*You guys are with me on never being big on A.J., right? I mean, dude just tried way too hard.

As a bonus, I’m going to mention one more savvy add. This AL outfielder, though, doesn’t fit into the same aging, injury-prone, power-hitting profile as the first three. In fact, he’s quite the opposite.

Desmond Jennings, Rays

Yahoo!: 10% I ESPN: 2.0%

Start typing “Desmond Jennings” into Google, and you’ll find that 1) the second autocomplete search is: “Desmond Jennings call up” and 2) there are nearly 140,000 results on that query. At this point, fantasy owners are fastening pictures of Rays GM Andrew Friedman to dartboards. The 24-year-old top prospect is slashing .280/.373/.479, and while he doesn’t have a ton of power, he’s got enough pop — his 10 homers at Triple-A are already one shy of his career high — to help in more than average, runs and stolen bases. Speaking of which, he’s swiped 15 of 16 this year, and he’s averaged 43 SBs in his four full minor-league seasons. There’s the other rub with Jennings: his health. He’s missed parts of seasons with back, shoulder, knee and wrist injuries. But so far in 2011, he’s been a-okay on the nicks-and-bruises front. While the Rays continue to trot out Sam Fuld and Justin Ruggiano in left, it’s not as if those two are good enough to block Jennings’ path to the bigs. Rather, there’s the fact that Tampa brass is doing all it can to avoid Jennings’ acquiring Super Two status, and since he’s already earned 33 days’ worth of service time from his debut last September, that has to be added onto whatever time he amounts this year to determine whether he gains the extra year of arbitration — a no-no for the cost-conscious Rays. The folks at Razzball did something along the lines of math, and guess what? June 28th — that’s today — marks the first day Jennings could be recalled and avoid Super Two. So there’s a more than fair chance Jennings makes his way to St. Pete in the next week or two. Add him now to be out in front of the rush.