Note: FanDuel is hosting a one-day Fantasy Baseball league tonight. It's $5 to enter and pays out $100,000 in cash prizes. First place wins $10,000. Sign up now!

We're about to close the book on the month of May, which means we are about to reach the expiration date on saying "it's too early" to judge a player's year-to-date performance. As gut-wrenching a decision as it may be, it could finally be time to sit some of the pitchers for whom you had high hopes back in March.

In this week's By the Numbers, we will take a closer look at half a dozen starters who appeared to be must-start options heading into this season. In the cases of two of them -- Stephen Strasburg and Jeff Samardzija -- you may have counted on them to serve as your rotation's ace. None of these pitchers has performed like anything resembling an ace. A deeper dive into their peripheral stats shows that some are worthy of benching. Yet despite close to two months of subpar performances, others present more hopeful signs.

Because of the high upside and long records of strong performance that each of these pitchers brings, none should be dropped yet in standard or shallow mixed leagues. In the worst cases, though, that could be a reasonable course of action if a turnaround doesn't happen soon.

Stephen Strasburg, Nationals (3-5, 6.50 ERA)

Of the disappointing pitchers featured here, none has been a bigger dud than Strasburg. Unfortunately for Fantasy owners, we can't simply write off his ERA and 1 for 9 quality start rate to bad luck or lack of run support. You wouldn't know it from Strasburg's 9.1 K/9 ratio, but he has been utterly hittable, allowing contact on 84 percent of the pitchers batters that batters have swung at (per FanGraphs).

Strasburg's swing-and-miss rate has swooned from last season's 12.5 percent to his current mark of 7.5 percent, and at the heart of the decline is his changeup. According to BrooksBaseball.net, he got whiffs on 26 percent of his changeups last season -- a mark that was right in line with his previous rates -- but so far in 2015, only 13 percent of his changeups have resulted in swings-and-misses. Strasburg's velocity hasn't fallen, and he's getting called strikes to make up for the lack of whiffs, but the additional contact he is allowing is taking a toll. He is clearly not a buy-low, and if you own him, he needs to ride the pine for now.

Anibal Sanchez, Tigers (3-5, 6.12 ERA)

After having allowed 13 home runs over the last two seasons combined, Sanchez is on the verge of topping that total within the first two months of this season. Through 10 starts, Sanchez has allowed 11 homers, which has played a key role in sending his ERA over 6.00. In fact, it seems to be the only thing that has changed substantially for Sanchez since last year. His velocity, whiff and strikeout rates and control are all at familiar levels.

Sanchez's ground ball rate had held steady between 48 and 49 percent in each of the previous three seasons, but this season it has plunged to 38 percent. The dip has been especially prominent on his changeup, as BrooksBaseball.net has his rate at 30 percent, after he recorded a 55 percent grounder rate on the pitch in each of the previous two seasons. This trend has persisted all season -- Sanchez has not induced more grounders than flyballs in any start this season -- so it's time to take it seriously. Outside of deeper leagues, there is no reason to start Sanchez at this point.

Mike Fiers, Brewers (1-5, 4.53 ERA)

Fiers posed a conundrum for owners early on this season, as he was piling up strikeouts at a rapid rate but was getting scorched whenever contact was made. His hard contact rate of 53 percent (per FanGraphs) was the highest in the majors during the month of April, and that made a bloated .439 BABIP, 5.79 ERA and 1.93 WHP somewhat believable. Heading into Wednesday's start against the Giants, Fiers' hard contact rate for May was only 33 percent, and his stats have shrunk accordingly.

Fiers has never been especially efficient, and his aversion to going deep into games is the only thing that keeps him from must-start status. He has lasted more than six innings or more only twice in 10 starts, but then again, he has allowed more than two runs only once in his last seven starts. As Fiers starts to pile up better performances, the window on a buy-low opportunity is quickly closing, but now is the time to make a play for him before his overall stat line starts to show the improvement.

Phil Hughes, Twins (4-4, 4.59 ERA)

Unlike Fiers, Hughes has been an innings muncher, going six-plus innings in all but one of his 10 starts. Hughes' owners would probably settle for an inning or two less per start if they could get Fiers' strikeouts. After averaging 8.0 strikeouts per nine innings last season, Hughes' ratio is down to 5.7 this year. While he has been allowing more contact, his HR/9 ratio has soared from 0.7 to 1.7.

Decreased velocity appears to be behind Hughes' lackluster performance. His average fastball velocity is down roughly 1.5 mph from the first two months of last season, and opponents have increased their Isolated Power off his fastball to .250 (excluding Wednesday's start against the Red Sox) after mustering just .130 for all of 2014. Though Hughes isn't allowing flyballs to travel significantly farther on average this season, he is getting hit hard frequently. According to BaseballSavant.com, only Aaron Harang and Jake Odorizzi have allowed more flyballs of a distance of 300 feet or more. In shallow leagues, if you haven't dropped Hughes yet, it's time. Without improvement, it won't be long before I'll be ready to do the same in 12-team mixed leagues.

Gio Gonzalez, Nationals (4-2, 4.53 ERA)

Just nine starts into the season, Gonzalez has already allowed five or more earned runs on three different occasions, yet he likely has the best chance to rebound of any of the pitchers included here. After a slow start, Gonzalez has been a reliable swing-and-miss pitcher, generating a 10 percent whiff rate over his last seven starts, and in two important regards, he has been far better than he has been in the past. Gonzalez is suddenly an elite-level ground ball pitcher, getting grounders on 60 percent of hit balls, and his long-standing control issues may be a thing of the past. Though he's never been better than average at throwing strikes, this season, he sports a 65 percent strikes-thrown rate.

A .380 BABIP rate has driven Gonzalez's WHIP up to 1.51, and a 28 percent line drive rate has much to do with those inflated stats. Line drive rates vary a great deal, and there is nothing in Gonzalez's statistical profile suggesting that he is likely to sustain such a high mark. Despite the ugly stats, Gonzalez remains close to a must-start option, and he presents a great buy-low opportunity.

Jeff Samardzija, White Sox (4-2, 3.84 ERA)

With three consecutive quality starts totaling 23 innings, Samardzija is clearly on the upswing. Still, he continues to be a little light on strikeouts and ground balls, so can we trust the improvement? Even from the difficult seven- start stretch that kicked off Samardzija's season to the tune of a 4.80 ERA, there were some positive signs. Excluding his season opener against the whiff-averse Royals, Samardzija went on to post a 10 percent swinging strike rate over his next six starts. His 7.8 K/9 ratio wasn't far off his typical rates, and it would have been higher if not for a 16 percent called strike rate.

An increase in flyballs remains a concern for Samardzija, but with stellar control and an ability to miss bats, he looks like a must-start options from here on out.