NEW YORK -- Mets reliever Daniel Herrera wasn't supposed to be at the MLB Fan Cave on Monday morning.

Herrera is 5-foot-6. He was selected by the Rangers in the 45th round of the 2006 First-Year Player Draft and originally offered $1,000 to sign. He throws the Majors' only known screwball, a 65-mph oddity that infuriates left-handed batters.

But the guy in the knit cap tossing sandbags in a friendly competition with MLB Dream Job winner Mike O'Hara was still around, now with his fourth Major League organization after being one of the two players to be named later by Milwaukee to complete the Francisco Rodriguez trade.

"Just do what you love," said Herrera, 26, when asked his message for aspiring players. "I grew up playing baseball all my life, and I never wanted to do anything else. I didn't let anybody stop me. All the short comments I heard growing up and trying to get to the next level didn't faze me at all. I wanted to do what I loved to do. That, mixed with a lot of hard work, you can do anything.

"I found my niche to play baseball and play in the Major Leagues, and I worked my tail off doing it. My message is, 'Do what you love and keep doing it.'"

It's a lefty-vs.-lefty niche, and Herrera has been a bright spot this month for the Mets. He made his New York debut on Sept. 2, entering the game at Washington with two outs in the ninth and striking out Jonny Gomes on a 2-2, 67-mph screwball to end the game. Herrera's WHIP with the Mets is 0.78, spanning 14 appearances out of the bullpen.

Herrera knows he will have to win a job again next spring, and it would seem the Mets will give him every opportunity. He rooms in an East Long Island apartment with Jason Isringhausen, with whom he played in the Reds organization. Herrera's brother recently moved to Brooklyn, so Herrera said he is looking forward to enjoying the New York life, a long way from his roots in Austin, Texas.

"Austin is a very different place than New York is. [It's] very musically sound, but as far as the traffic and everyday life here, it's a lot different," he said. "I'm going to have to pace myself, get a faster pace for this New York lifestyle, but I'm loving it."

One thing he is looking forward to is a lot more time to chat with John Franco, the former Mets reliever. Isringhausen was chatting with Franco the other day in the clubhouse and introduced Franco to Herrera. They briefly discussed the screwball, a pitch that served Franco well during his 21-year career.

Short list
Mets reliever Daniel Herrera is the shortest active player in Major League Baseball.
Player Team Height
Daniel Herrera Mets 5'6"
Jose Altuve Astros 5'7"
Tim Collins Royals 5'7"
Alexi Amarista Angels 5'8"
Tony Campana Cubs 5'8"
Chone Figgins Mariners 5'8"
Mike Fontenot Giants 5'8"
Rafael Furcal Cardinals 5'8"
Johnny Giavotella Royals 5'8"
Josh Harrison Pirates 5'8"
Maicer Izturis Angels 5'8"
Aaron Miles Dodgers 5'8"
Antoan Richardson Braves 5'8"
Jimmy Rollins Phillies 5'8"
Matt Young Braves 5'8"

"There's not many of us," Franco told him. "You've got to search for them."

Herrera is definitely unique in Major League Baseball. For one thing, he's the shortest active player. When asked exactly how tall, he said: "5-foot-6. I used to say 5-foot-8 just to hype myself up a little bit, but everybody I'd meet would say, 'No way you're 5-foot-8.' You know, I don't lie anymore. It's 5-foot-6. It's short enough."

Secondly, he is the only screwball pitcher in the Majors, or at least the only one publicly acknowledged. Oakland's Dallas Braden said he threw one during his perfect game in 2010, but he reportedly has abandoned it.

"I don't throw very hard, I throw mid-80s," Herrera said. "[I've] got some breaking balls and cutter and sinkers, but my main pitch is a screwball. Nobody throws it anymore. Especially coming from a left-hander, it's a lot different view for the batter than he's ever seen. It's just a lot about deception from me. My main pitch is screwball, and it comes in about 65, so about 20 miles an hour slower than my fastball. It's a good moving pitch for me, and I throw it often.

"I don't really know of a pitching coach who teaches it. There's been a few who have thrown it. As far as teaching it, it's not really a standard pitch. It's an off-ball pitch. Basically, to kind of help protect guys' arms, too. It took my elbow and shoulder quite a while to deal with it. I just don't think it's out there, and not a lot of people teach it."

Herrera said he stumbled upon the pitch during his career at the University of New Mexico, which was the only Division I college to offer him a scholarship -- half academic, half athletic.

"I had a terrible changeup in college," he said. "I just kept pronating and pronating until it kind of spun over the top like a curveball. So it was a lot of trial and error trying to get a changeup into my game in college. One thing led to another, and I kind of found it. Nobody really helped me with the mechanics of it or how to throw it, it was just trial and error. I pronated my arm enough to where it moved a lot, and I stuck with it."

The Rangers drafted him in the 45th round in 2006 and offered him $1,000 to sign. He said he negotiated with the Rangers and got them up to $20,000 to sign, "which was significantly more than I thought I could get." So he decided to forgo his senior year at New Mexico.

Herrera's greatest obstacle in the Majors so far would seem to be his inability to retire right-handed batters. During his rookie season, in 2009, he held lefties to a .183 average, while it was .361 for righties. That's a pretty wide spread. Reds manager Dusty Baker said at that time:

"He just has to figure out how to make the adjustment against righties. Those guys have hit him hard. You have to get through uncharted waters and places that you haven't been through before in order to know how to do it when you get back there, which is next year."

After a big step backward in 2010, struggling with command and confidence, Herrera was claimed off waivers by the Brewers this May. He was effective at Triple-A Nashville, and appeared in two games for Milwaukee. The Mets needed another lefty in the bullpen, so he was sent packing again.

Despite his impressive WHIP, Herrera has still allowed lefties to hit .214 against him and .350 for righties. It's easier to accommodate that niche role after the Sept. 1 roster expansion, so time will tell.

"I had a great time playing over there [in Cincinnati], from 2008 to early this year. Dusty Baker and a lot of those guys, they're awesome," he said. "I had a great time with that organization. [Monday's series opener at Citi Field] is the first time I'm going to step across the field from them, so it's going to be a fun series.

"The season has been a lot of moving around for me. I started with the Reds in Spring Training, got moved to the Brewers, and now to the Mets, so it's been a difficult time as far as kind of moving around and going where I'm needed, but I'm finally here in New York. I love it here and I'm excited."

Of O'Hara's 11-10 victory in the sandbag toss at the back of the Fan Cave, Herrera hung his head in mock frustration and said: "Crushing defeat."

"It's a great setup here," he said. "[You've] got pool tables, you got a barber shop, just a great place to hang out. Unfortunately, I played a game of [sandbags] and lost. I had to play on a Yankee board, too, so it was a little bit more defeating. I'll come back."