Explaining Mariano's contact rates from 2009

It is no secret that Mariano Rivera’s average velocity on both his four-seamer and his cutter was down last season. Now that he is a full year removed from shoulder surgery, an issue that seemed to hinder his arm strength for much of 2009 and cause, in part, the downturn in pitch speed, we have a reason to be optimistic about his velocity going forward. However, if his velocity remains in its current range, or falls further, there is reason to wonder about his effectiveness over the course of a new contract, which he will seek after entering free agency at the end of the year.

Some may decry the notion that Rivera’s loss in velocity impacted his year – he did pitch exceptionally well, as he usually does – but, believe it or not, Rivera’s minor decrease in pitch speed did manifest itself in his contact rates. In fact, Rivera had some of the higher contact rates in the American League a season ago. In the spirit of Alice in Wonderland, the following is a nice 3D bar chart – I love me some bar charts, man – that showcases this relationship.

Rivera’s career average velocities for his fastball (purple bar) and his cut-fastball (blue bar) are featured on the left (in mph) and, as you can see, in 2009, on the right, the two pitch speeds are down a few mph – 91.8 and 91.3 – in comparison. Conversely, but not coincidentally, the amount of contact hitters made on Rivera’s pitches outside of the zone, i.e., O-Contact% (green bar), and the amount of contact hitters made on Rivera’s pitches inside of the zone, i.e., Z-Contact% (red bar), both experienced significant increases – O-Swing of 73.2% and Z-Swing of 90.2% – when compared to the career numbers (O-Swing of 61.7% and Z-Swing of 85.9%). From this, it seems reasonable for one to then ponder a possible connection between Rivera’s downturn in velocity and his upswing in contact percentage. Essentially, when your pitches are not really as fast as they once were, there is more time for hitters to react to them.

This, of course, could relate to pitch movement, too, rather than just velocity. Rivera’s decrease in pitch speed was likely brought on by a lack of arm strength throughout the season, and this issue seemed to simultaneously lessen the movement on his fastball and cut-fastball. In 2009, according to pitch f/x, the vertical movement (up) on Rivera’s fastball was 4.83 inches and the horizontal movement (lateral, in right-handers) was 0.74 inches. Both numbers were well below average. For comparison, in 2008, Rivera’s fastball rose 7.52 inches and broke in on righties at 1.54 inches (below average but not like in 2009). That signals a significant loss of movement on the fastball which probably explains why Rivera rarely used it last season, throwing it only 7% of the time, according to FanGraphs.

The cutter, the pitch Rivera used 82% of the time last season, also experienced a loss of movement. In 2008, its vertical rise was 7.21 inches – slightly less than the average mark for that year – and its horizontal movement (in on lefties, away from righties) was 2.52 inches, a mark which was well above average. However, in 2009, its vertical rise was 6.22 inches and its vertical movement was 2.12 inches. The vertical movement was a bit below average, about an inch below, but the horizontal break was still VERY good, despite the stated loss in year-to-year movement.

This, then, the decrease in Rivera’s pitch velocity and movement explains the marked increase in his contact rates (I looked at command, too, but his BB/9 of 1.63 was still under his career mark of 2.11). The two negative trends were likely brought on by the shoulder surgery Rivera had last winter that impacted his arm strength, but I’m sure age had something to do with it, as well (to a smaller degree). Some may say, well, if his velocity and pitch movement was down, and his contact rates were up, why was he still so effective in 2009? That is a valid question, of course, and I think it is mainly because Rivera has done away with his fastball in order to use the cutter almost exclusively. Even with the lesser movement last season, the movement was still great, which says a lot about the pitch. More contact was made, a notion evidenced further by Rivera’s higher than usual line drive rate – 21.8% in 2009, up from his career mark of 16.8% – but his peripherals were still above average across the board. Rivera seemed to realize the lack of velocity issue and went with more movement instead, though the cutter had less movement than it did in the past.

As I said at the outset of this novel, if the decrease in velocity remains, or continues, it might cause some concern when Rivera enters free agency and is looking for another contract. Those concerns are understandable, as the velocity change would impact Rivera’s game, a point made by his contact rates in 2009. However, he has clearly adapted well to his current abilities, and remains as effective as ever. He’s a robot, with or without a 96 mph fastball.

Photo by Reuters