Every team is optimistic at this time of the year on their chances to make a deep run into the postseason, and while it's difficult to predict who will be aggressive in improving their team prior to the July 31 non-waiver Trade Deadline, we know that every year there is at least one team that makes a big leap forward, such as the 2015 Mets and the '16 Indians.
Here are three teams I expect to make a major jump in the win column this year, mostly because I think their respective pitching staffs are better than people realize:
Pirates (2016 record: 78-83)
Normally one of the top pitching staffs in the National League, the injury bug devastated the Pirates' rotation in 2016, and the front office decided to trade closer Mark Melancon and starter Francisco Liriano and push the restart button for '17. With staff ace Gerrit Cole back and healthy, there is plenty of reason to be optimistic.
Jameson Taillon has dominant stuff and is ready to take the next step in his development as the Bucs' No. 2. Ivan Nova's heavy sinker returned under the tutelage of pitching coach Ray Searage, and he saw his success in the NL rise along with his two-seamer usage, as he got his ground-ball rate back above 50 percent for the first time since '13. Youngsters Tyler Glasnow (Pittsburgh's No. 1 prospect, per MLBPipeline.com) and Chad Kuhl should take another step forward. Glasnow's command has been spotty, but he has electric stuff, while Kuhl fills out the bottom part of the rotation by pounding the strike zone with his low-90s fastball and slider.

With No. 3 prospect Mitch Keller's quick rise through the Pirates' system and possible Major League appearance later this summer, look for Pittsburgh to dangle Glasnow or Kuhl with its position player prospects and add an experienced starter like Jose Quintana. If that happens, the Bucs are a real threat to challenge any club in the NL.
Astros (2016 record: 84-78)
The Astros' rotation has not been getting a lot of love this year, but they pitched better in 2016 than many people give them credit.
Granted, Dallas Keuchel looked human compared to his 2015 season, but he recently told me it took him close to two hours to get ready for his starts due to shoulder irritation. Seemingly healthy, mentally and physically, look for him to return to his ace status of two years ago, when he won the American League Cy Young Award. Keuchel is off to a good start, having allowed only one run through two starts.

Lance McCullers's season was cut short due to injury as well last year, and this offseason, he changed his delivery and arm action, allowing him to bounce back better between starts. With his electric stuff and hopefully better command, he is the X-factor, and his first start (one run allowed over six innings with seven striekouts) is encouraging.
Joe Musgrove and Mike Fiers should eat up innings, Musgrove showed enough promise in 2016 to project him as a solid number No. 3 starter if his command continues to improve, while Fiers will fill important backend innings as Collin McHugh works his way back from elbow troubles that will keep him out until June.
All that said, Houston's rotation could use another No. 2-type starter, particularly with McHugh's uncertain status. General manager Jeff Luhnow was ultra-aggressive in adding significant offensive pieces to the team including free agents Josh Reddick and Carlos Beltran, and trading for catcher Brian McCann. Along with the Pirates, the Astros are a likely suitor for Quintana.
Mets (2016 record: 87-75)
I know this comes as no shock, but the Mets have a ridiculous wealth of arms, and despite a series of injuries to Matt Harvey, Jacob deGrom, and Steven Matz, they still reached the 2016 postseason thanks in most part to the dominance of Noah Syndergaard and the poise of their youngsters like Robert Gsellman and Seth Lugo.
Syndergaard is scary good -- one earned run allowed through two starts -- and has added a wipeout changeup that should allow him to continue his dominance, while deGrom's mechanical tweak has allowed him to pitch more freely, and consequently his fastball velocity has returned to the mid-90s form of two years ago.

Zack Wheeler appears healthy from his Tommy John surgery that cost him the past two seasons, and he impressed the organization enough to make their rotation at the start of the season. Unfortunately, Matz has continued with more health issues -- this time, a bulky elbow has him on the shelf to start the season -- and Lugo has a partially torn UCL and hopes to avoid surgery. That said, with a staff of seven-plus legitimate starters as his disposal, manager Terry Collins should have plenty of depth to overcome any long-term injuries, and this team should be neck and neck with the Nationals all season as they battle for the 95 wins it will likely take to win the NL East.