CHICAGO -- Some familiar issues plagued the Rays during their 4-2 loss to the Cubs on Monday night at Wrigley Field. Their typically stellar defense made a few costly mistakes. They struck out 12 times and struggled to capitalize on some key opportunities at the plate. They lost for the sixth time in their last eight games, falling to 5-6 on the year.

One issue the Rays haven’t had is the performance of Opening Day starter Shane McClanahan, who was as dominant as he’s ever been in their series opener against the Cubs.

McClanahan piled up a career-high nine strikeouts, didn’t walk anybody and allowed only two runs (one earned) over six efficient innings. He left with the game tied at 2-2, and Tampa Bay fell behind in the seventh when reliever Jason Adam hit Seiya Suzuki before lefty Jeffrey Springs gave up a go-ahead RBI single to Ian Happ.

But McClanahan looked every bit like an ace in the making throughout his third start of the season, giving the Rays one silver lining on another frustrating night.

“He was awesome,” Rays manager Kevin Cash said. “Mac is doing some special things here through three starts.”

McClanahan has been doing it for the better part of a year, too. In his last 20 starts since June 15, the day after Rays ace Tyler Glasnow exited a start against the White Sox with what wound up being a season-ending right elbow injury, McClanahan has posted a 2.92 ERA with 123 strikeouts in 104 2/3 innings.

The Cubs were quite impressed after McClanahan struck out nine of the 21 batters he faced and forced them to swing and miss on 13 of his 80 pitches. Take it from Chicago manager David Ross, whose squad faced the Brewers' trio of Corbin Burnes, Brandon Woodruff and Freddy Peralta to begin the season.

"That guy tonight they had was really good,” Ross said. “We've faced some really good pitching so far this year. This guy's probably one of the best we've faced."

If nothing else, McClanahan is also one of the boldest. With a feels-like temperature of 34 degrees at first pitch and winds whipping out to right field, the 24-year-old took the mound wearing short sleeves. He was the only Tampa Bay player not bundled up for the cold -- or the snow flurries that swirled around the ballpark all night.

“You’re not going to change anything up,” McClanahan said. “It's just snow.”

McClanahan’s evolution into a well-rounded pitcher, not just the high-velocity thrower he might have been viewed as when he was a prospect, was on full display Monday night. He didn’t necessarily bring the heat on a frigid night in The Friendly Confines, as the fastball that often touches triple digits maxed out at 97.1 mph while averaging 95.7 mph.

But he consistently baffled the Cubs with curveballs (he threw 24), changeups (18) and sliders (16). Facing an entirely right-handed lineup, he finished eight of his nine strikeouts with curveballs and the other with a changeup. And he pounded the zone by throwing 72.5 percent of his pitches for strikes.

“I think it was just trusting my stuff, not trying to make it do anything more than it needs to do,” McClanahan said. “Just consistently trying to fill up the zone and attack and get ahead.”

In doing so, McClanahan put together the Rays’ longest start of the season. They entered the night as one of only two teams, alongside the Rangers, without a start of longer than five innings. Their last six-inning start before McClanahan’s came last Sept. 18, when Ryan Yarbrough went six against the Tigers.

McClanahan was more economical getting 18 outs on Monday than he was in his last start, when he threw 85 pitches over 4 2/3 innings against the A’s on Wednesday. Cash indicated McClanahan could have worked into the seventh if not for the abbreviated Spring Training schedule, their starters’ deliberate build-up to this point and Chicago’s cold-weather conditions.

“We're probably another start or two away from sending him back out there again and adding more pitches, but he gave us every opportunity,” Cash said.

For his part, McClanahan said he was “so locked in” that he didn’t even realize he’d pitched six innings for the first time this year.

“If you'd have told me it was the fourth, I would've believed you,” he said. “I think I figured out a lot. Obviously still a lot to work on and improve, but I think I'm in a good spot going forward.”

McClanahan’s only mistake came in the second inning. After typically sure-handed shortstop Taylor Walls committed his third error of the season and allowed Suzuki to reach safely, McClanahan served up a 420-foot, two-run homer to Patrick Wisdom on a fastball down in the zone.

“I felt good, you know, considering it was snowing,” McClanahan said. “Tough game. That's how it is. One mistake, but I thought I did a lot right.”