MINNEAPOLIS -- Let's think back to the world of two months ago, when the Trade Deadline was fast approaching and many around Twins Territory were debating which relievers on the open market would be Minnesota's magic fixes for a bullpen that, for many on the outside, appeared to be the weak point of the team.

But Twins chief baseball officer Derek Falvey maintained that he expected most of the club's bullpen help to come from within.

"Are there pieces that could potentially help that are external? Yeah," Falvey said on July 24. "But, I think, by and large, most of the production is going to come from the team that is already here. We all expect the deadline to be when you make or break your team. I don't subscribe to that idea because a lot of it comes from what we have."

He was right.

The Twins did make deals for Sergio Romo and Sam Dyson before the deadline passed, and Romo has been a key member of the relief corps -- and the clubhouse -- since his arrival in Minnesota.

But the consolidation of the bullpen has come, in large part, to the season-long progress of arms like Tyler Duffey, Trevor May and Zack Littell, whose development has been the driving force in making the bullpen a reliable strength of this team in the second half.

"I think the likes of Tyler Duffey and Trevor May and others, at that time, were probably going through some ups and downs during the course of the season, but have stepped into those roles," Falvey said last week. "We knew they had the stuff. We knew they had the ability. Now it's just harnessing all of it with the command and attacking. Since that time, each of those guys have done that and we've had guys step up for one another."

"The first person you always point to when you're giving credit is the pitcher and the player himself," Twins manager Rocco Baldelli said. "But on top of that, I think our day-to-day, our process, the work that's put in, the thought that's put into everything that's going on, and the choosing of the players and the belief in them and giving them the opportunities, it all matters."

So, what has that work been? Let's take a closer look.

Tyler Duffey
Second-half stats: 0.99 ERA (3 ER, 27 1/3 IP), 43 K, 8 BB
How he's done it: The last time Duffey allowed a run was July 23. Seriously. Since then, he has thrown 22 2/3 scoreless innings over 25 appearances, with 38 strikeouts.

One of the converted starter's keys has been relying more on his four-seam fastball up in the zone and pairing it with his breaking ball down, which "tunnel" well together to keep hitters guessing when the ball comes out of his hand. After throwing his four-seamer only 36.7 percent of the time last year, he's using it 51.3 percent of the time in 2019, with a slightly refined grip that he feels has added some movement to the pitch.

Duffey said it took him some time to get a feel for where the top of the strike zone was, and being able to get back down to the bottom of the zone when he needed to, but since he's gotten more comfortable with executing his spots, he's become one of the best relievers in the Major Leagues.

In his own words: "I came in and they told me, 'Here's where you get swings and misses. Attack. Use these pitches as you need to and maybe dial back usage on some others and in other counts.' Things like that. ... Towards the end of spring, it felt pretty good, and then obviously, in [Triple-A] Rochester, I got it really dialed in and I never looked back. Because when you work on something and you get the results that you're looking for, then you're going to embrace it even more and keep going."

Zack Littell
Second-half stats: 1.25 ERA (3 ER, 21 2/3 IP), 19 K, 4 BB
How he's done it: Since Littell was converted to a full-time relief role in Triple-A Rochester in June, the 23-year-old has been scoreless in 22 of his 25 appearances in the Major Leagues, with three earned runs allowed in those 25 games.

Littell has taken well to simplifying his arsenal and relying on his two strongest offerings in the four-seam fastball and the slider. He has essentially scrapped the sinker, curveball and changeup that he used as a starting pitcher last season and essentially splits his usage evenly between the slider and the fastball, which has gained nearly two miles an hour in velocity since he has been moved to shorter stints.

As a starter, he would try to establish one of his pitches early in outings so he could pitch off that in the late innings. As a reliever, he feels he can just attack with whatever he has working on any given day. He doesn't always have the feel of both of his pitches, but one offering is usually good enough on any given day that he's still able to make it work.

In his own words: "Going into the bullpen, it's kind of, 'Here's everything I have.' There's not as much of feeling hitters out. It's just coming in and getting out of the inning. The difference is as a starter, you kind of have to go in and establish one pitch, whether it's a fastball or breaking ball, establish that pitch early, and pitch off that for six, seven innings. As a reliever, it's just coming in and getting guys out."

Trevor May
Second-half stats: 3.00 ERA (10 ER, 30 IP), 41 K, 9 BB
How he's done it: There's the May of the first three months of the season, and then there's the May 2.0 of the present. Through the end of June, the right-hander had 30 strikeouts and 17 walks. Since then? Try 47 strikeouts and nine walks. So, what's changed?

Behind the scenes, May was working hard to fix some elements of his mechanics. When analyzing the biomechanics of May's motion, the Twins discovered that the 30-year-old had very low hip mobility. As May pointed out, that's not uncommon among pitchers, but his case was particularly pronounced. He worked through drills and exercises to improve his hip mobility, but incorporating that into his delivery threw his upper body out of whack.

So, then, more exercises came to reinforce the feeling of keeping May's upper body closed while his hips moved, and once May felt comfortable with that in Oakland in early July, he said that his command, velocity and execution all jumped, and he hasn't looked back. He even threw "a TV hunge" -- a velocity reading of 100 mph on television -- in August. (It was actually 99.8 mph, but he counts it anyway.)

In his own words: "Me specifically, with a lot of the work I was doing mechanically coming to fruition, it allowed me to throw the ball over the plate and keep it a little bit more simple with how I'm attacking hitters. It gave me more confidence in those pitches. All that spells being able to come back from behind and not make very many misfires. I think that Duffey and [Taylor Rogers] really never walked many guys. Honestly, the only one really inflating those numbers was me. When I stopped walking guys as much, I think the numbers dropped quite a bit."

Taylor Rogers
Second-half stats: 3.95 ERA (12 ER, 27 1/3 IP), 37 K, 3 BB
How he's done it: Rogers is honestly confused by the charts showing that he's relying on his slider more and his curveball less often this season. The way he sees it, he's been doing the same thing that he did at the end of last year, when he first discovered the slider and became one of the best relievers in baseball.

So, for the left-hander, who is again one of the elite relievers of the game this season, there hasn't been much of a conscious adjustment in how he's been attacking hitters. Instead, he feels he's made more mental progress this season as he has embraced the closer role that he more concretely adopted in June.

Though the Twins' bullpen has been defined by its fluidity in roles throughout the season, Rogers admitted that it was tougher for him to settle into the mindset that he needed at the end of games when he was unsure when he would be used. He also admitted that he felt he deserved the closer role earlier in the season, too. Since he settled in, though, he's learned a lot about himself and his day-to-day preparation in that mindset of a closer to get to this point in the season.

In his own words: "Just the fact that there's nobody behind you. There's nobody to come save you. There's not another inning for us to maybe score or tie the game or whatever. Once you're in there, that's the last of the line. It's tough to deal with until you've dealt with it. It's one of those things where it kind of has to be your day-to-day mentality, and I think that was tough for me early on in the season, because I wanted to have that mentality, but I also needed to have the mentality of maybe throwing the seventh. I think once I was able to set my mental state, that really helped."