There’s no more fickle existence in Major League Baseball than that of a relief pitcher. Teams are generally more willing to tinker with their bullpens than their benches, and often need to make changes to account for overworked staffs.

But the tumult also brings opportunity. Relievers who are throwing well at the right moment can find themselves right back in the majors. And there are often wide-open Spring Training battles to be joined and won.

Plenty of relievers signed minor-league deals last winter. And a solid number of them ended up on MLB rosters within the first two months of the season. Despite failing to receive MLB guarantees on the free-agent market, these ten hurlers have provided quite a bit of value in the early going:

Matt Albers, Nationals: With the Nats’ pen struggling badly, Albers has been a desperately need source of reliable frames: 16 2/3 innings of 1.62 ERA ball. A strong 57.8% groundball rate and meager 1.6 BB/9 walk rate tend to support the results, though Albers isn’t getting enough whiffs (7.6 K/9) to keep up quite this level of pitching.

Craig Breslow, Twins: The lefty specialist has been everything the Minnesota front office hoped for when it bought into his new-look delivery over the winter. Like Albers, a minimal BABIP (.217 in this case) helps explain the sub-2.00 ERA, though in both cases the solid early work is enough to entrench these pitchers in their respective pens for the time being.

Jorge De La Rosa, Diamondbacks: A long-time starter, De La Rosa has averaged less than one inning per relief appearance in Arizona. But the results of that change in focus have been quite promising. It’s good enough that De La Rosa carries a 50% groundball rate with 8.8 K/9 and 3.5 BB/9, supporting a 2.35 ERA through 15 1/3 frames. But there could be more in the tank, as he’s also averaging a career-high 94.1 mph with his fastball and generating a huge 19.5% swinging-strike rate.

David Hernandez, Angels: Though he has completed just 11 innings thus far, after making his debut later than most of the names on this list, Hernandez has impressed. He’s showing the same kind of velocity and swinging-strike rates that made him a buy-low option last year for the Phillies, but the real question is whether he can continue to avoid the long balls that have plagued him in recent years.

J.J. Hoover, Diamondbacks: It was anyone’s guess whether the former Reds’ late-inning stalwart would rebound, but he’s showing well through fifteen frames in Arizona. Hoover is walking more than five batters per nine, but has also racked up 12.6 K/9 (on a career-high 12.6% swinging-strike rate) and owns a 3.00 ERA. So far, a new pitch mix (more two-seamers and sliders) seems to be working.

Jason Motte, Braves: After beating out Hernandez to become the next veteran reclamation project in Atlanta, Motte has ascended to the majors and helped stabilize the pen. His peripherals aren’t terribly inspiring — 6.4 K/9, 3.2 BB/9, 53.1% groundball rate — but the results (1.59 ERA) have been there through 11 1/3 innings.

Bud Norris, Angels: The crown jewel of the Halos’ impressive slate of finds, Norris has thrived in the closer’s role that he took over out of necessity. Through 23 2/3 innings, he carries a 2.66 ERA with 11.8 K/9, 3.4 BB/9, and a 44.2% groundball rate. Norris is bringing more velocity (94.1 mph fastball) and swinging strikes (13.2%) than ever before.

Yusmeiro Petit, Angels: The veteran long man has been stellar, delivering 28 1/3 staff-preserving innings of 2.54 ERA ball through 16 appearances. Petit is carrying 9.5 K/9 against 3.2 BB/9 on the year. (As if the trio of arms on this list weren’t enough, the Halos have also benefited from the strong work of Blake Parker, who had been outrighted off the 40-man roster over the winter.)

Anthony Swarzak, White Sox: There are some very strong performers on this list, but perhaps none has been quite as impressive as Swarzak. He has given the South Siders 19 2/3 breakout innings of 1.37 ERA ball, with 10.1 K/9 and just 0.9 BB/9 in that span. At present, he’s working at a 19.8% swinging-strike rate — about double what he carried over the prior two campaigns — making him quite an interesting potential trade candidate this summer.

Jacob Turner, Nationals: Though he isn’t carrying sparkly numbers, Turner has been an important contributor in D.C. He’s functioning in the swingman role that Petit occupied last year, providing 21 2/3 innings (over two starts and six relief appearances) of 3.74 ERA pitching thus far. While Turner is averaging only 5.8 strikeouts and 3.3 walks per nine, he is continuing to carry the velocity boost he showed last year. Interestingly, he is now working in the zone far more than ever before (50.2% versus 42.1% career average) — though it’s also important to note that his swings and misses are way down (4.8%).