SEATTLE -- The buzz surrounding Frankie Montas as one of baseball’s most sought-after pitchers ahead of the Aug. 2 Trade Deadline has only heightened with each start. However, an early exit on Sunday now leaves his immediate future in question.

On a cold Seattle afternoon with heavy rainfall in the surrounding area at the first pitch, gloom came over T-Mobile Park’s visiting dugout as the A’s saw their ace depart Sunday’s 2-1 loss against the Mariners after just one inning with tightness in the back of his right shoulder. 

There was an immediate cause for concern with how Montas’ stuff looked in the first. Surrendering a leadoff homer to Julio Rodríguez as part of a 13-pitch frame, Montas maxed out at just 94.5 mph with his fastball, a pitch that had reached as high as 99.1 mph over his previous two outings. Overall, Montas’ velocity on his four-seamer was 2.4 mph slower than his season average, while the velocity on his sinker was 2.7 mph lower.

After an evaluation of Montas’ shoulder by team doctors revealed some inflammation, he is expected to undergo an MRI when the A’s return to Oakland on Monday to determine the severity of the issue.

“Frankie went out in that first inning and we noticed that the velo was down,” said manager Mark Kotsay. “We checked in with him after he came in and he had some tightness and just didn’t feel like he could get fully extended. In that situation, we’re gonna err on the side of caution.”

Montas noted that an inability to recover the way he normally does after a start following his outing at Yankee Stadium earlier in the week may have been a contributing factor to Sunday’s alarming situation. While the soreness felt no different to what he’s experienced throughout the year, seeing his velocity readings on the stadium radar gun was an uneasy feeling for both Montas and the A’s training staff, leading to a joint decision to end his outing.

“I’m always sore,” Montas said. “Usually I’ll go out there and pitch and it gets better. But my velo has never been down. I felt like the best thing was to come out of this game and take a better look at [the shoulder].”

Emerging as a workhorse for the A’s who has ranked among the AL's leaders in innings pitched over the past two years, Montas has managed to avoid a stint on the injured list as a Major Leaguer for the entirety of his seven big league seasons. Initial strength tests revealed no sign of a major injury. While Monday’s MRI will provide a better idea of how much time, if any, he might have to miss, Montas remained positive about his outlook postgame.

“I’m going to get the MRI when we get back home and we’ll just go from there,” Montas said. “I don’t think it’s anything bad, just soreness and maybe some inflammation. Nothing that I’m worried about.”

Though the A’s entered a rebuild this spring by trading away several stars, they held off on dealing away Montas in hopes of receiving a better offer during the season. Based on the right-hander’s numbers, that move appeared to be the right one. Entering Sunday, Montas held a 3.20 ERA over 16 starts. Among American League starters, Montas had ranked fifth in innings pitched (95 2/3), seventh in strikeouts (99), eighth in WHIP (1.09) and 12th in opponents’ batting average (.226).

For a scuffling last-place A’s club that entered the day off to its second-worst 80-game start to a season (26-54) since moving to California in 1968 and on pace to lose an Oakland record 110 games, Montas has been one of the few bright spots as a potential All-Star candidate. For a young A’s clubhouse that often looks to Montas for leadership, losing him for any amount of time would certainly be a blow.

“He and Paul [Blackburn] have been our aces this year,” said A’s shortstop Elvis Andrus, who homered on Sunday. “Hopefully, it’s nothing serious. Maybe just a little bit of swelling and he’ll be back on the mound, because we want him. Every time he or Pauly is pitching, we know we have a high probability of winning that day. I want all my teammates to be healthy. I hope it’s nothing crazy and he can be back pretty soon.”