Chris Davis eyes the flight of his grand slam in the eighth inning that gave the Orioles a 9-5 win over Minnesota in their home opener on Friday. The opposite-field blast made Davis the fourth player to homer in each of the first four games of a season. (Rob Carr/Getty Images)

For much of the past decade and a half, opening day in Baltimore has been an exercise in make-believe, a day for everyone to get dolled up in orange and black for one spring afternoon, cram into Oriole Park at Camden Yards, pretend there is hope for that year’s Orioles and imagine what it might feel like to see the charade made real as spring turns to summer, and summer to fall.

But on Friday afternoon, the 46,653 who sat in the warm sunshine and cheered for the Birds didn’t need to pretend or imagine. This was what it feels like to have real hope in early April, and for once, a stirring, comeback victory on opening day didn’t seem destined to serve as the high point of the Orioles’ season.

On a day that felt like a seamless carryover from last September, the Orioles rallied behind slugger Chris Davis for five runs in the eighth inning to secure a 9-5 victory over the Minnesota Twins. Davis, in the midst of an historic opening week, hit a go-ahead grand slam on the first pitch he saw from Twins reliever Tyler Robertson to account for the final margin.

“There are a lot of good things going on in here,” Davis said at his locker after the game. Reflecting on the curtain call he took after the grand slam and the standing ovation he received as he jogged back out to first base for the top of the ninth, he said, “This is a great place to play. I had chills running back out on the field.”

In the first four games of the Orioles’ season, Davis has amassed a good month’s worth of production, with four homers and 16 RBI — with the latter figure exceeding by 33 percent the previous MLB record for RBI in a season’s first four games (12, held by three players). Only three other players — Willie Mays, Mark McGwire and Nelson Cruz — have homered in four straight games to start the season. Dating to the end of 2012, Davis has 11 homers in his past 11 regular season games.

“There’s a pretty good chance,” deadpanned Baltimore Manager Buck Showalter, “he won’t be able to keep up this pace.”

Midweek forecasts of cold and rain gave way to cloudless skies and 60 degrees Friday, as the Orioles paid pregame homage to the memory of beloved ex-manager Earl Weaver, the Hall of Famer who died in January and whose jersey number (4) is painted in the grass near the home dugout and stitched onto the right sleeves of the team’s uniforms. In a video tribute shown on the stadium scoreboard, the Orioles paid tribute to their next-door neighbors, the Baltimore Ravens, for their Super Bowl title.

This was the rare opening day here — the first since 1998, in fact — where last season was worth savoring one last time and where last season’s win total was a worthy goal for the season ahead. In 2012, Baltimore was one of the biggest surprises in baseball, tossing aside 14 straight losing seasons to claim a wild-card berth with a 93-69 record — highlighted by a remarkable 29-9 record in one-run games.

The Orioles of 2013 have cast themselves as a franchise full of self-belief, having built upon the success and goodwill of 2012 by doing next-to-nothing to improve themselves over the ensuing months — all but ignoring the winter’s thin free-agent market and making only minor tweaks to their roster. Thus, they entered 2013 with largely the same team that ended 2012, banking that a full season of phenom Manny Machado added to the holdover mix of homegrown talent and secondhand imports would be enough to get them back to the playoffs.

Baltimore went 33-18 last year after the August day when Machado was promoted from Class AA straight to the majors, and on Friday, at age 20, he became the youngest Oriole to start for the team on opening day since Boog Powell in 1962. Even Cal Ripken had to wait until he was 21.

It was Machado’s sacrifice bunt — with two on and none out in the decisive eighth inning, and the Orioles trailing by a run — that unleashed the chain of events that brought the game to Davis. In calling for the bunt, Showalter figured (correctly) that Twins counterpart Ron Gardenhire would walk Nick Markakis to load the bases, bringing Adam Jones to the plate and Davis to the on-deck circle.

Jones singled home the tying run off right-hander Casey Fien, and after Gardenhire brought in the left-handed Robertson, Davis whipped his bat at a first-pitch slider on the outer half of the plate and muscled the ball the opposite way, over the wall in left.

“I’ve never seen anything like it,” Orioles starter Jake Arrieta said of Davis’s sizzling start.

But as the fans streamed out toward Eutaw Street and into the night, for once there was every reason to believe they would be seeing more of the same for these next six months.