There are 10 qualified starting pitchers with an xFIP under 2.80 in the last 30 days.

Among them are predictable names like Chris Archer (2.52), Clayton Kershaw (2.53), Chris Sale (2.64), Johnny Cueto (2.74), and Zack Greinke (2.76).

The other five aren’t as well known, and therefore, they are more intriguing.

Being in the top 10 xFIP leaderboard for a month is not necessarily a huge accomplishment. However, xFIP has one of the highest correlations with future ERA of all pitching metrics, so it’s among the most relevant numbers to examine when searching for potential breakouts or analyzing the legitimacy of poor or plus performance.

Below is a table sorted by the top 10 qualified starting pitchers in xFIP over the last 30 days*, with the best statistic in each category highlighted in yellow, and the worst statistic in each category highlighted in red:

Top 10 xFIP Leaders, Last 30 Days Name IP K% BB% HR/FB GB% ERA FIP xFIP Jimmy Nelson 32.2 30.5% 4.6% 9.5% 48.8% 1.93 1.95 2.27 Trevor Bauer 31.2 32.3% 6.2% 20.8% 48.1% 4.26 3.21 2.47 Chris Archer 34.0 33.3% 7.8% 8.7% 53.1% 3.97 2.11 2.52 Clayton Kershaw 41.2 30.0% 5.0% 17.2% 51.0% 1.94 2.88 2.53 Jeff Samardzija 32.2 27.9% 0.7% 12.5% 40.0% 4.13 2.50 2.61 Chris Sale 38.1 35.2% 5.7% 10.5% 35.9% 4.70 2.27 2.64 Tyler Anderson 29.2 27.8% 7.1% 23.5% 55.8% 3.94 3.45 2.70 Johnny Cueto 39.0 29.8% 4.4% 17.1% 38.8% 3.92 3.18 2.74 Zack Greinke 35.2 34.4% 6.1% 15.6% 45.5% 3.03 3.02 2.76 Luis Severino 35.2 27.0% 6.8% 10.0% 60.6% 2.02 2.54 2.79

Well then. Jimmy Nelson has been good lately. And how about Jeff Samardzija’s walk rate? Chris Archer seems to have solved last year’s home run problem. Tyler Anderson, meanwhile…

There are numerous takeaways from this table. Instead of sporadically breaking down every noteworthy item, let’s do it on a case-by-case basis. There are five obvious aces on this list (Archer, Kershaw, Sale, Cueto, Greinke), and then there’s everybody else.

Jimmy Nelson, Trevor Bauer, Jeff Samardzija, and Tyler Anderson all have career ERAs north of 4.00. Luis Severino’s is 3.93. Their xFIPs in the last 30 days suggest they might be better. Let’s analyze each one individually:

Jimmy Nelson: The numbers don’t lie. Nelson has the best ERA, FIP, and xFIP among qualified starters in the last 30 days. He sports a strong 3.36 ERA/3.03 FIP/3.39 xFIP in 64.1 innings this season, despite a career line of 4.25/4.26/4.25. Nelson’s strikeout rate of 24.3% this year is up from a career rate of 18.5% before the season. His PITCHf/x average fastball velocity this year is 94.2 mph, up from 92.9 mph last year and 93.3 mph the year before. His sinker, slider, curve, and changeup have all seen similar upticks in velocity. Nelson looks like he’s having a breakout year in his age-27/28 season (his birthday was yesterday), and the numbers suggest he’s worth an add in most formats.

Trevor Bauer: The unorthodox righty entered 2017 with a pedestrian career strikeout rate of 21.4%, and a 4.42 ERA/4.24 FIP/4.28 xFIP. This year, however, Bauer has a 29.1% K-rate that’s sixth in all of baseball and second best in the American League behind Sale. Bauer’s only problem has been a susceptibility to the long ball (he’s allowed 11 home runs in 58.2 innings), but his 2017 HR/FB ratio of 20.4% is nearly double his 11.7% career average. While other fantasy owners may steer clear of Bauer because of his unsightly 5.83 ERA and track record of mediocrity, his peripherals scream breakout and he’s a very nice buy-low candidate.

Jeff Samardzija: Similar to Bauer, Samardzija’s career strikeout rate was just 21.3% entering 2017, yet it’s 28.9% this season. Strikeout rates have risen every year since 2005 (except from 2014 to 2015, when they were the same to one decimal place), but the difference over the last three years is just +1%, and the difference from last year to this year is just +0.4%. So Bauer’s and Samardzija’s strikeout rate jumping up eight and seven percent, respectively, isn’t explained by the league-wide increase. Meanwhile, Samadrzija has simply stopped walking people, as his third-best-in-baseball 3.4% walk rate indicates. Also similar to Bauer, Samardzija’s been victimized by the home run. He’s currently running a career-high 14.9% HR/FB ratio, but he plays half his games in one of baseball’s most pitcher friendly parks. Expect Samardzija to get better in that category, and if he does, he becomes a borderline elite pitcher if the high strikeout rate persists. He’s definitely someone to target in fantasy leagues, especially if owners are turned off by that 2-7 record and 4.29 ERA.

Tyler Anderson: Anderson pitches for the Rockies, and Rockies pitchers frequently pitch at Coors Field. That’s bad. Anderson was placed on the 10-day disabled list Sunday with left knee inflammation. That’s also bad. Remarkably, Anderson has actually pitched better at home than on the road in his career, so he has a clean 3.84 ERA/3.61 FIP/3.57 xFIP at Coors and has allowed just 1.0 HR/9 there in 105.1 innings. In 69 career road innings, however, Anderson has a 5.09 ERA/4.78 FIP/3.84 xFIP and has given up 1.7 HR/9. After allowing just 12 home runs in 114.1 innings last season, good for a stingy 0.94 HR/9, Anderson has allowed 13 long balls in 60 innings this year, which comes out to 1.95 HR/9. Anderson had success last year by holding opponents to a 12.4% HR/FB rate, but a rough beginning to 2017 has brought his career HR/FB rate to 16.6%. Even though he boasts a strong 48.7% career ground ball percentage, it’s just really hard for a Rockies starting pitcher to be a strong fantasy asset.

Luis Severino: Paul Swydan wrote about Severino’s breakout season on Monday. He noted that Severino has found success not by lowering his HR/FB rate, which is virtually identical to last year’s, but by creating a wider gap in velocity between his fastball and his secondary pitches, which has led to more strikeouts, and by inducing more (and weaker) ground balls against right-handed hitters. Indeed, Severino’s strikeout rate has jumped to 27.5% this season, fifth-best in the AL, and his K-BB% is second-best only to Sale. His 54.5% ground ball rate is the fifth-highest in the AL, and, as Swydan notes, his 16.7% increase in GB% from last year to this year is the highest in all of baseball. Severino, 23, looks like a breakout star in the making, and he’s undoubtedly worth owning in all formats. He probably won’t come cheaply, though, given his sterling 2.90 ERA/3.14 FIP/2.86 xFIP.

*The table was updated before games on Monday, June 5, and the rest of the stats in the article are current before games on Tuesday, June 6.