Corey Kluber was erratic in his Red Sox debut

Corey Kluber took the mound for the Boston Red Sox on Opening Day but his performance didn't live up to the expectations of an ace leading this rotation.

The right-hander was shelled for five earned runs while failing to escape the fourth inning against the Baltimore Orioles on a Thursday afternoon at Fenway Park.

Much of the damage came as a result of the long ball. Kluber threw an 87 mph sinker to Orioles catcher Adley Rutschman that didn't sink nearly enough. The pitch stayed near the middle of the plate and Rutschman blasted it to deep right field for a solo shot that put the O's on the board in the first inning. In the fourth inning, Ramon Urías caught a cutter up in the zone and deposited it into the Monster seats for a two-run homer.

Kluber allowed 2+ home runs in a game only twice last season. His only appearance during his one-year stint with the Tampa Bay Rays in which he allowed more than two home runs was when he allowed three in a loss to the Red Sox last August.

Red Sox starter Corey Kluber struggled with his control

Kluber's command wasn't sharp in his first start of the new season. He threw 48 of his 80 pitches for strikes. Kluber led the league with a 1.2 BB/9 last season but he didn't showcase that same level of control in this game, issuing four walks in only 3 1/3 innings. He walked more than two batters in a game only once last season, a start last April in which he walked four against the Orioles.

The fourth free pass sent manager Alex Cora strolling out from the dugout to take the ball from Kluber with one out in the fourth inning. Zack Kelly inherited a bases loaded mess and almost immediately uncorked a wild pitch that allowed one of the runners to score. Kelly walked a pair of batters, the second of which pushed in a run with the bases reloaded, charging Kluber with his fifth earned run. Kluber put the Red Sox in a tough spot by putting the ducks on the pond to begin with but Kelly's own control problems made the final line on Boston's starter even uglier than it should have been.

His five-pitch arsenal relied mainly on his sinker, curveball and cutter, with a changeup occasionally mixed in and a seldom-used four-seam fastball. His sinker sat in the 87-88 mph range, per Baseball Savant. Kluber isn't the mid-90s power pitcher he was back in his heyday but this is still a slight dip from the 88.9 mph he averaged with the pitch last year. We shouldn't expect him to crank up the heat much higher than this but his velocity still isn't quite where he needs it to be.

If there's a silver lining to Kluber's outing, it was encouraging to see him collect four strikeouts in less than four innings of work. Kluber's 7.6 K/9 last year was a career-low and far from the 9.5 K/9 that he's averaged for his career. He probably won't return to striking out over a batter per inning but he showed that he still has the ability to make batters miss, generating six Whiffs. The Orioles lineup was mediocre in terms of strikeout rate last season, with a 23 K% that was the 13th-highest in the majors, per FanGraphs. This wasn't merely a case of Kluber picking on a strikeout-prone lineup.

The Red Sox signed Kluber to a one-year, $10 million deal with an $11 million option for 2024. His team debut went horribly wrong but better days are ahead for the two-time Cy Young award winner. Kluber, who turns 37 years old next month, is clearly past his peak but that doesn't necessarily mean he's met his expiration date. He showed signs of some control issues during an otherwise solid spring. His track record suggests we should expect him to regain his command, at which point he can still be a useful asset to this rotation.

Despite giving him the nod for Opening Day, the Red Sox aren't counting on Kluber to be their ace. A healthy Chris Sale will still be the best pitcher on this staff, but Boston wanted to ease him in without the pressure of Opening Day weighing on a pitcher who has missed most of the last three seasons due to injuries. Garrett Whitlock and Brayan Bello started the season on the injured list but aren't expected to miss significant time.

Kluber could conceivably be the fourth-best starter in this rotation when everyone is healthy. If his results resemble what he delivered for the Rays last year, the Red Sox will have gotten their money's worth.