One of the best parts about this time of year in Major League Baseball is the optimism permeating from all 30 clubs.
Before any regular-season games are played, every team can dream big and envision its best-case scenario coming to fruition. While reality eventually sets in for many clubs, every year sees a few exceed expectations.
This season, the three teams below could do just that. The common thread between them? Each has a rotation that may be better than many realize.
St. Louis Cardinals (83-79 in 2017)
After ranking among the top 10 in fWAR (fourth), innings (sixth) and ground-ball rate (fifth) last season, St. Louis' rotation could take a step forward in 2018. Leading the group again is Carlos Martínez, who has established himself as one of the top starters in the National League and possesses the potential to reach even greater heights. Lance Lynn is gone, but Miles Mikolas could be a worthy replacement. Although Mikolas owns a lifetime 5.32 ERA and 1.42 WHIP in the Majors, he's a far different pitcher now than he was in his previous big league trial. The right-hander made great strides in Japan, posting a 2.18 ERA with a 0.99 WHIP over three seasons.

The Cardinals should also benefit from having Luke Weaver in the rotation for a full season after he recorded a 3.88 ERA with a 72-to-17 K/BB ratio across 60 1/3 innings in 2017. The owner of a career 1.99 ERA in the Minors, Weaver is a major breakout candidate in 2018. And while neither Adam Wainwright (5.11 ERA) nor Michael Wacha (4.13) had an impressive ERA in 2017, both pitchers' FIP marks (4.29 for Wainwright, 3.63 for Wacha) suggest they were a bit unlucky.
Prospect Alex Reyes is a wild card -- he is expected to return from Tommy John surgery at some point during the first half -- but he may be placed in the bullpen so the club can limit his workload.
Toronto Blue Jays (76-86 in 2017)
After the Blue Jays led the American League in ERA in 2016, their '17 season went awry as Aaron Sanchez battled persistent blister problems, and Marco Estrada struggled to the tune of a 4.98 ERA (3.30 ERA over '15-16). Sanchez went 15-2 with an AL-best 3.00 ERA over 192 innings in '16, so his frequent absences were particularly detrimental.
Toronto could have one of the best 1-2 combinations in the AL if Sanchez can make a healthy return in 2018, with Marcus Stroman seemingly coming into his own as a frontline starter. Stroman produced a 3.09 ERA over 201 innings in his age-26 season, and has tossed at least 200 frames in each of the past two years. J.A. Happ gives the Blue Jays a dependable third option, as he's posted an ERA no higher than 3.61 while making at least 25 starts in each of the past three seasons.

Estrada is a reasonable rebound candidate, posting a 3.68 ERA last September after reportedly fixing the sleep troubles that may have contributed to his struggles (6.85 ERA) from June through August. And though Jaime García is coming off a 4.41 ERA, he will likely be a more dependable fifth starter than Francisco Liriano was last year (5.88 ERA over 18 starts with Toronto).
Minnesota Twins (85-77 in 2017)
While the Twins were one of last year's surprise contenders, making the playoffs after finishing with the worst record in baseball during 2016, they achieved that success in spite of their rotation. Minnesota had seven hurlers make at least nine starts in 2017 -- five recorded an ERA of 4.50 or higher. But thanks to the additions of Lynn and Jake Odorizzi, the club will be relying heavily on only one (Kyle Gibson) of those seven pitchers in 2018.
Lynn and Odorizzi aren't aces, but they have both proven to be durable rotation assets throughout their careers. Odorizzi has made at least 28 starts in four straight years while posting a 3.81 ERA in that span. And although Lynn missed all of 2016 while recovering from Tommy John surgery, he made at least 29 starts in every season from 2012-15, before returning to post a 3.43 ERA over 33 starts last year.

The Twins' rotation will again be headlined by All-Star Ervin Santana (3.32 ERA over 2016-17) once he returns from offseason right-middle-finger surgery, though youngster José Berríos has the potential to be the club's true ace. Berrios showed great promise in 2017 -- recording a 3.89 ERA with an 8.6 K/9 rate over 145 2/3 innings -- and he's still just 23 years old.
And while Kyle Gibson has produced a 5.07 ERA in two straight seasons, he did provide some reasons for optimism by notching a 3.57 mark across his final 12 starts in 2017.