Troy Tulowitzki returned to Coors Field last night for the first time as a visiting player, facing the Rockies nearly 11 months after the blockbuster trade that sent the five-time All-Star shortstop from Colorado to Toronto. Because the Blue Jays went 31-10 with Tulowitzki in their lineup last season and made the playoffs for the first time since 1993 the trade was immediately labeled a success, but Tulowitzki didn’t actually play all that well in those 41 games and his contract meant neither team involved was viewing the deal as strictly a short-term move. Tulowitzki’s mediocre performance has continued this season, which has to be worrisome for the Blue Jays given that he’s 31 years old and signed through 2020 at an average annual salary of around $20 million.

When the Blue Jays acquired Tulowitzki they did so knowing that his raw hitting numbers would decline because that’s just how things work with Rockies hitters. Coors Field undeniably boosts offense, often to extreme degrees, and hitters departing the Rockies can generally be counted on to post less gaudy raw numbers in their new homes. However, projecting how Rockies hitters will fare elsewhere can be tricky due to a potential “hangover” effect playing home games at altitude can have on a player’s performance in road games. In other words, it’s not always as simple as taking a longtime Rockies hitter’s road numbers and penciling those in as his overall numbers, because the road numbers might be underrepresenting his true, non-Coors Field talent level.

Tulowitzki spent the first decade of his career calling Coors Field home and took full advantage, hitting .321/.394/.558 in 526 games there compared to .276/.349/.468 in 522 road games. Even with a hangover effect possibly dragging them down those road numbers alone would have made Tulowitzki the best-hitting shortstop in baseball from 2006-2015, so the Blue Jays gladly would have signed up for .276/.349/.468. Instead he’s hit just .226/.306/.405 in 95 games following the trade, including .214/.294/.423 in 54 games this year. Once the king of good-hitting shortstops, his .717 OPS ranks 15th among the 26 players who’ve logged at least 50 games at the position this season and Tulowitzki is the third-oldest player in that group. His post-trade fall is magnified even further by the emergence of a potentially historic group of young shortstops.

Shortstops aging out of the position defensively in their 30s is common and Toronto probably felt pretty secure knowing that Tulowitzki’s bat would fit just fine lower on the defensive spectrum if needed some day. However, his defense has actually remained strong in Toronto, with positive Fielding Runs Above Average marks in both seasons. His power hasn’t disappeared either, with 16 homers and 16 doubles in 95 games for a .179 isolated power that’s right in line with his .192 isolated power on the road as a member of the Rockies. He’s still playing good defense and still hitting for plenty of power, so what’s missing from Tulowitzki’s game since the trade? His once-outstanding ability to make consistent contact and control the strike zone has abandoned him.

Tulowitzki has never been a particularly patient hitter, drawing 53 non-intentional walks per 600 plate appearances for the Rockies. That part of his game hasn’t changed, as his walk rate in 95 games for the Blue Jays extrapolates to 50 in 600 plate appearances. What has changed in his strikeout rate, which was once very low for a power hitter. Tulowitzki averaged just 96 strikeouts per 600 plate appearances for the Rockies and his road strikeout rate of 103 per 600 trips to the plate was only slightly higher. He’s already whiffed 95 times in 95 games for the Blue Jays, which works out to 141 per 600 plate appearances. Or, put another way: Tulowitzki has struck out about 40 percent more often for the Blue Jays than he did for the Rockies, even on the road.

That’s an awful lot of plate appearances ending in strike three that once resulted in balls in play, and that issue is compounded by the fact that when Tulowitzki has put the ball in play for the Blue Jays he hasn’t seen many of them fall for hits anyway. Since the trade, his batting average on balls in play is .262, which is 60 points below his overall Rockies career mark and 40 points below his road-only Rockies career mark. During the past calendar year, 173 big leaguers have at least 450 plate appearances and Tulowitzki is 156th in BABIP, with nearly all of the 17 players worse than him being slow-footed catchers, designated hitters, and first basemen. The combination of leaving Coors Field, striking out 40 percent more often, and ranking 156th in BABIP is a fool-proof recipe for turning a .300 hitter into a .230 hitter.

There’s little chance of his BABIP remaining so dreadful long term, so that alone is reason to trust in a bounce back of some kind arriving soon enough. However, prior to the trade, his strikeout rate was already trending in the wrong direction and that stands out as the biggest red flag. He struck out just 16 percent of the time for the Rockies, including a strikeout rate below 18 percent in every season from 2008 to 2014 and a strikeout rate of 15 percent of lower in half of those years. Then last season his strikeout rate rose to 21 percent in 87 games for the Rockies before the trade and went up even further to 23 percent for the Blue Jays after the move. This season he’s whiffed 24 percent of the time.

He’s not swinging more often or swinging at more pitches outside the strike zone, but rather just making less contact and less-solid contact when he does swing. In particular, Tulowitzki has had below-average production versus fastballs in both seasons with the Blue Jays after feasting on fastballs throughout his Rockies career. Toronto has been the place for right-handed hitters to thrive in recent years, turning journeymen into sluggers and strong hitters into stars, yet the Blue Jays have not found a way to tap into what made Tulowitzki so great for the Rockies and instead have seen his production plummet at 31. There’s reason to believe things will improve, but more reason to believe his time as an elite shortstop with a middle-of-the-order bat may already have passed right around the time the Blue Jays decided to make him part of their long-term plans.

His average exit velocity since joining the Blue Jays has hovered around 89-90 miles per hour, which is underwhelming considering the MLB average is 89.2 mph this season. Tulowitzki has made up for the mediocre exit velocity by increasing his launch angle, which is how he’s kept hitting for power, but in general not hitting balls very hard and the specific decline in production against fastballs certainly seems to point to a loss of bat speed and overall ability. That could be due to normal aging, but it may also have been brought about sooner than normal as a result of his numerous injuries over the years. He can still crush mistakes, but on a game-to-game basis his ability to put the ball in play with authority has seemingly vanished.