After a dominant spring, many hoped Julio Teheran had turned a corner. His disappointing 2012 campaign was attributed to a variety of mechanical changes, but offseason reports suggested Teheran had corrected those flaws. His tour of the Grapefruit League appeared to validate winter reports, as he struck out 35 batters in 26 innings and posted 1.04 ERA. While Teheran’s spring was cause for optimism, his first start of the regular season didn’t go so well, and the performance suggests there’s still more work to be done.

Last season, we discussed Teheran’s inconsistencies. Entering 2012, Teheran was ranked FanGraphs’ fifth best prospect in baseball, but he struggled to live up to the hype. To pinpoint the cause of his problems, I watched a random start from the 2011 season. On July 26 against the Durham Bulls, Teheran’s fastball velocity sat 93-95 MPH and frequently neared triple digits. His curveball, while erratic, showed promise. It featured a tight 11-5 break and, when thrown well, caused the Triple-A Rays to flail. His changeup was his best offering. After he established his fastball, hitters were helpless against his low to mid 80s changeup. His three pitch arsenal was electric and justified Marc Hulet’s ranking. Here are a couple of GIFs of Teheran pitching against the Mets in September of 2011, so you can see the movement for yourself.

In 2012, Teheran was a different pitcher. When I watched him in August, the first change to standout was mechanical. His tempo – the momentum of a pitcher’s body when delivering the ball to the plate – slowed and his arm action was rigid. As his tempo slowed, so did his velocity. His overpowering fastball velocity was now merely 88-90 MPH with little movement. Later on that month, Teheran increased his tempo and his velocity crept up to 92-93 MPH, but the explosiveness had not returned. His breaking ball no longer looked like a curveball; instead its shape resembled an early breaking slider.

After Teheran’s impressive Spring Training performance, I gleefully turned on the his start against Chicago to see the changes Teheran made. With the caveat that it was just one start, his start against the Cubs had mixed results. His tempo was faster and his arm action was more fluid than it was when he struggled last year. As his tempo increased, his velocity did too. His fastball velocity averaged 91.5 MPH and touched 95 MPH. Further, the Braves had worked with Teheran to make his delivery more natural. The 22-year-old demonstrated better command of the pitch, which allowed him to get ahead of Cubs hitters. On Saturday he threw 17 first pitch strikes and put eight Cubs in an 0-2 hole.

When Teheran maintained elite velocity in 2011, his delivery was high effort. To an extent, one has to defer to the organization decision to rein him in. The Braves have watched each start and analyzed each pitch since Teheran was 17. In hindsight, it’s not surprising a 21-year-old would struggle as he alters his mechanics for the future. But, the mechanical changes aren’t without consequences. Teheran is still slower to the plate than he was in 2011 and he may never regain his lost velocity. Further, on Saturday, his four-seam fastball lacked noticeable backspin and arm-side run. Without more movement, his four-seam fastball does not grade out better than average. The offering will “play up” due to his command and hitter’s respect for his changeup. Thankfully, Teheran has committed to his two-seam fastball. It’s wise to incorporate a two-seamer to induce groundballs because hitters are unlikely to swing and miss at his four-seam fastball.

Teheran’s breaking ball continues to be a concern. The pitch still resembles a slider and its quality is poor. Against the Cubs, Teheran recorded one swing and miss on the 23 breaking balls he threw. The new offering breaks too early and does not feature enough vertical tilt to go along with its significant horizontal movement.

Note the difference in movement compared to the curveball from 2011, above. Also, notice how much he has slowed down.

His use of this breaking ball was, at best, strange. Generally, sliders have a large platoon split and shouldn’t be used frequently against opposite handed batters. However, Teheran featured his breaker against lefties, throwing eight of them compared to just four changeups. Not only is his changeup a better offering than his breaking ball, but changeups do not have a platoon split for most pitchers. If Teheran continues to deploy a fastball/slider combination against lefties the results will be disastrous, as they were on Friday night, when they hit .417/.417/1.083 against him. Hopefully, Teheran will incorporate his best pitch into next outing’s game plan to get left-handed hitters out.

The breaking ball was ineffective against right-handed hitters too, due to its early and one plane break. The Cubs were able to recognize the pitch early and Teheran was unable to induce a single whiff. After seeing this offering this and last year, I’m generally unimpressed. It’s thrown more consistently – shape, command and velocity – than his former curveball, but those attributes lack utility if hitters don’t swing and miss at it. Of course, he needs to continue to throw it in games if it’s going to develop, but he should rely more on changeup and two seamer against right-handed hitters. It’s said pitchers shouldn’t throw same handed batters a changeup, but pitchers with elite changeups don’t conform to that principal. For instance, James Shields has thrown his changeup 24% of the time to right-handed hitters. Even if using the pitch is counter to conventional wisdom, Teheran should at least mix the pitch in to support his other offerings.

In this start against Chicago, Teheran did not demonstrate significant growth from last year, but there were positives. The uptick in his velocity and his improved command are indicators of progress. The biggest highlight was his reliance on his two seam fastball, which could be a plus offering. However, his reluctance to use his changeup was baffling. Against right-handed hitters the decision left him with three pitches – an average four seam fastball, a below average breaking ball, and the new two seamer. Further, his preference for his breaking ball against left-handed hitters caused him to be ill-equipped to get outs. Teheran will continue to underwhelm as a back of the rotation starter if he does not gain confidence in his changeup. However, if Teheran incorporates his changeup with his two seamer and improving command, he could still wind up as a solid mid-rotation arm.