Mariners lefty James Paxton has long tantalized fans and coaches with glimpses at his potential. Injuries and inconsistency has kept him from realizing it. Is 2017 his breakout year?

Mariners left-handed starter James Paxton has been up and down most of his career in Seattle. The Ladner, Canada native has never stayed healthy long enough to eclipse the career-high 121 big-league innings he tossed last year.

Many thought last season would Paxton’s breakout for the Mariners. He was entering his age-27 season. He had seen big-league hitters before and held his own. He had dominated at times in AAA Tacoma.

Then Spring Training happened. Paxton threw batting practice in the Cactus League, forcing Mariners manager Scott Servais and his coaching staff to roll with the solid but unimpressive Nathan Karns in the rotation to start the year.

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And so began the season-long pitching turnover that eventually doomed the Mariners to just miss the playoffs yet again. To end the 16-year drought, they’ll need Paxton to take the next step. Is he ready?

For their part, the Mariners coaching staff has been supportive and positive about Paxton up to this point.

“He is one of the guys ready to take the next step and be a real anchor in our rotation,” Scott Servais said.

Paxton spent the start of 2016 in Tacoma working on his delivery with Tacoma Rainiers pitching coach Lance Painter and turned in several quality starts after he was recalled to the Mariners. Painter’s suggestions, which included a slightly lower arm angle, according the Tacoma New Tribune’s John McGrath, translated into consistently higher fastball velocity last season, and it showed in the numbers.

Paxton has always been a hard-throwing lefty, a coveted MLB asset for any team. But last season, his average fastball velocity jumped from 94.1 Miles Per Hour in 2015* to 96.7 MPH. That’s an incredible adjustment.

The faster fastball translated into higher strikeout rates for Paxton in 2016, from a ho-hum 7.5 K/9 in 2015 (according to Baseball Reference) to an 8.7 K/9 last season. According to Fangraphs, Paxton induced swinging strikes on 11.7% of his pitches, up from 7.2% in 2015.

Another way Paxton missed bats last season was his cutter. He threw the cutter far more for the Mariners than ever before. A whopping 15.7% of his pitches last season were cutters, up nearly 12% from 2015, and averaging 89.9 MPH. Painter’s tweak in Paxton’s delivery is likely the culprit of the action his cutter now has (i.e. it cuts into the hands of righties and away from lefties). His new delivery probably also contributed to better command. He dropped his walk percentage from 9.8% in 2015 to 4.7% in 2016.

Paxton had a 3.79 ERA in his 121 big-league innings last season, but his Fielding Independent Pitching (FIP) was only 2.80. An improved defense behind him, particularly in the outfield, should help him bring his ERA down.

The only under-the-hood metric I can see in 2016 that doesn’t suggest Paxton will break out for the Mariners this year is a high Batting Average of Balls in Play (BABIP). Normally, when I see a high BABIP against a pitcher, I attribute it to bad luck or bad defense, but Paxton’s .347 mark against him seems to be bolstered by the higher percentage of line drives he allowed last year. Opposing hitters had a 21.9% line drive percentage against Paxton last year, up from 17.2% in 2015. That line drive percentage is close to Paxton’s MLB career mark of 20.5% in 286 innings.

So hitters still squared up Paxton’s pitches at about the same rate as previous seasons despite the new delivery. Still, Paxton’s career numbers are solid overall, an 18-15 record with a 3.43 ERA. If he can continue missing bats at a similar pace to last year and outfielders Jarrod Dyson, Mitch Haniger, and Leonys Martin run down a few more of those line drives, Paxton has a path to greatness this year if he can stay healthy.

Paxton is only 28, young enough to shake off previous injury problems with the right luck and conditioning. Based on early throwing sessions in Spring Training this season, he looks like he’s on his way to being an effective second or third starter in the rotation, a position he’s never had going into the regular season.

Will Paxton take the next step? I think he can keep his ERA close to the 3.00 mark with a healthy strikeout rate and WHIP. What are your projections for Paxton?

*Paxton’s average fastball velocity in 2014: 94.4 MPH. 2013: 94.3 MPH. Amazing what a slight tweak in arm angle can do.