By Steve Keating

TORONTO (Reuters) - In 100 years of baseball at Fenway Park, Boston Red Sox fans have seen many highs and lows, but the team's flat start to the season may sting more than usual with the city prepared to mark a special occasion.

Following a 3-1 loss to the Toronto Blue Jays on Wednesday, the Red Sox return to Boston for their home opener with a 1-5 record that has not exactly left Beantown in a party mood for next week's centennial celebration of Fenway Park.

America's oldest ballpark has survived worse calamities, including an 86-year World Series drought, last year's slightly more woeful 0-6 start followed by a season-ending collapse that cost them a playoff berth.

But as Boston prepares to take on the Tampa Bay Rays in their home opener on Friday and host the hated New York Yankees on April 20 for Fenway Park's official 100th anniversary, Red Sox Nation seems more ready to panic than party.

"I don't know (how the fans will react)," Boston pitcher Jon Lester said after taking the loss in his seventh career complete game despite allowing just three hits and striking out six Blue Jays in eight innings. "Hopefully it's good, hopefully they see that we're grinding it out leaving everything on the field.

The problems behind Boston's early struggles to the 2012 Major League Baseball season are many.

Boston limped into the new campaign with a number of key injuries, losing closer Andrew Bailey to a thumb injury while Japanese starter Daisuke Matsuzaka continues to recover from surgery on his right elbow.

Slugger Carl Crawford is also not ready to return to the lineup after undergoing left wrist surgery and new manager Bobby Valentine has already faced criticism for some of his decisions.

The Red Sox have shown plenty of grit with late-game rallies - one of which produced a 4-2 win over the Blue Jays on Monday - but have mostly lamented a lack of early run production that has left starting pitchers digging out of holes.

Players insist the one thing they have not lacked is effort but that was not enough to lift the mood in a glum clubhouse as the Red Sox quietly packed for the trip home.

"We might be losing games but guys aren't dogging it out there," Red Sox third baseman Kevin Youkilis said after going hitless in four at-bats on Wednesday. "Guys are busting their asses, guys are trying."

Following the four-game set with the AL East-leading Rays, the Red Sox host the AL champion Texas Rangers for two games before the weekend visit by the rival Yankees.

"We're not worried about the teams we're playing against, we just worry about playing the game," said Youkilis. "this is the Boston Red Sox. You watch us over the years and we are always in it."

(Editing by Frank Pingue)