It's a rare thing when a baseball player learns plate discipline on the fly at the Major League level. Often, a hitter's ability to be selective at the plate is something that is inherent. Sure, it can be a learned skill sometimes, but it's more often than not that a player either has an innate sense of when to swing or he doesn't.

This is not the case for Philadelphia's Odubel Herrera, who dedicated himself over the offseason to walking more and seeing more pitches at the plate. So far, so good.

Herrera is second in the Majors in walks, with 17 in 19 games. Only Paul Goldschmidt (18) has more. Last year, he didn't receive his 17th walk of the season until August 27th. He walked just 28 times in 537 plate appearances in 2015. This year, he's on pace for 153 walks. He's taken a base on balls in 21.0% of his plate appearances this year, second in the Majors, behind just Colby Rasmus (21.3%). Last year, he walked in just 5.2% of his plate appearances, 112th out of 141 qualified Major League hitters.

All those walks aren't for show. They've translated into a .432 on-base percentage, eighth in Major League Baseball. His slash line of .286/.432/.429 gives him a wRC+ of 132. He's hit 2 homers, has 9 RBI, 11 runs scored, and 4 stolen bases. And in the Phillies' win over the Brewers on Saturday night, Herrera became the first player in Phillies history to score four runs, hit a homer, and steal two bases in the same game.

Amazingly, Herrera is owned in just 11.0% of ESPN leagues, so if he's available, go grab him. He'll provide you with a little pop, some stolen bases, and a ton of on-base opportunities hitting lead-off for the Phils.

Here are some other waiver wire suggestions for Week 4 of the MLB season.

Jake Lamb - Arizona Diamondbacks (3B)

ESPN Percentage Owned: 28.1%

Jake Lamb is a decent power hitter who can provide some pop against right-handers at third base. He's off to a hot start this season, slashing .281/.373/.516 in 75 plate appearances, with 2 dingers, 10 RBI, and 8 walks. Here he is showing off some wheels by smoking a triple against the Giants in San Francisco this week.

Lamb will sit against the tougher left-handers in baseball, but he's a strong play against right-handers, which is what the vast majority of pitchers in baseball are anyway. He's seen his walk rate jump from 9.2 to 11.3% this year, while his strikeout rate has fallen from 24.9 to 21.1%. And, the power that had been missing from his bat his first two season is there so far early this year.

If you need help at third base, Lamb could be available.

Scooter Gennett - Milwaukee Brewers (2B)

ESPN Percentage Owned: 24.4%

Is Milwaukee's Scooter Gennett for real? He hit his fourth blast of the season on Sunday against Philadelphia and has 14 runs scored, with a slash line of .258/.361/.516 and a wRC+ of 128.

There is some reason for caution, however. Three of his four homers were hit in the first five games of the season, and his walk rate has jumped dramatically from 3.1 to 14.7% last year to this year. Gennett also hit just 6 bombs in 391 plate appearances last year and never reached double figures in any minor league season.

He's worth an add for now, especially if you're desperate for a second baseman with some offensive potential. But beware: the bubble could burst.

Rick Porcello - Boston Red Sox (SP)

ESPN Percentage Owned: 25.1%

Rick Porcello is having a bit of an odd season for the Red Sox.

He strikeout numbers are crazy, 11.17 batters per nine innings, way up over last year when he K'd 7.80 per nine, and way, way up over his career average of 5.89. He's won all three of his starts this year but has an ERA of 4.66 and a FIP of 4.72. 

Here he is in his last start, against the Rays, in which he struck out nine in seven innings.

I'm not overly confident Porcello is going to remain a high strikeout guy moving forward. His average fastball velocity so far this year is 89.5 miles per hour, down from 91.0 a year ago. But for the moment, he's someone to stash on your bench in deeper and AL-only leagues.

Hector Santiago - Los Angeles Angels (SP)

ESPN Percentage Owned: 38.4%

Quick, raise your hand if you realized Hector Santiago made the AL All-Star team last year. I don't see many hands raised.

In 32 starts, he put up an ERA of 3.59 and a FIP of 4.77, striking out 8.07 batters per nine and walking 3.54. This year, his success has continued, thanks to lowering his walks per nine innings (2.70) and increasing his strikeouts per nine innings (9.11). His 2.70 ERA and 3.89 FIP are also better than last year

He's one of the more underrated starters in baseball, potentially making him available in your league.

Drew Pomeranz - San Diego Padres (SP)

ESPN Percentage Owned: 29.7%

Hi everybody. I'd like to introduce you to Drew Pomeranz, strikeout machine.

Pomeranz has been dealin' so far this year, striking out 12.74 batters per nine, far above last year's 8.58 and his career 8.32 batters per nine innings. His control is a little haywire, walking 4.58 batters per nine, but it hasn't hurt him yet, with a 2.04 ERA and a 2.50 FIP.

Here he is striking out 10 Pirates this week. And that ain't easy.

In his age-27 season, pitching in pitcher-friendly Petco Park, Pomeranz could be heading for a breakout season -- if he can get his walks under control.

Yasmani Grandal - Los Angeles Dodgers (C)

ESPN Percentage Owned: 31.2%

There really is only one elite catcher, Buster Posey. The rest are all just different shades of the same player, at least in fantasy circles. So chances are, you already have a half-decent catcher on your roster. 

But if you do not, Yasmani Grandal has been pretty darn good this year. He's slashing .320/.485/.480 with 4 doubles in just 33 plate appearances this year, but he's walked in 24.2% of his plate appearances so far and struck out just 6.1% of the time.

And it's not all out of the blue. Grandal was good last year for Los Angeles, slugging 16 homers in 426 plate appearances with a 115 wRC+, 47 RBIs, and 43 runs scored.

Stash him on your bench if he's available.