The grind of a 144-game season will usually, over time, weed out the pretenders from the contenders, often with ruthless precision.

While any baseball season is littered with peaks and valleys, some extremes being higher or lower than others, there are usually signs throughout that hint at which teams fall into which category.

We don’t yet know if the Tohoku Rakuten Golden Eagles are contenders or pretenders. The Eagles certainly entered the year with the glint of a contender, with ace Masahiro Tanaka returning to lead a talented, young rotation, and new signings Andruw Jones and Casey McGehee bolstering the offensive arsenal.

The Eagles haven’t resembled a team with title aspirations lately, and especially not after swooping into Chiba on Friday, looking to snap out of a funk that had seen them lose seven of 10 games, and limping back to Sendai Sunday smarting from the aftereffects of a three-game sweep at the hands of the Chiba Lotte Marines.

“We gave up the lead and lost in all three games,” Eagles manager Senichi Hoshino said during a news conference after the series finale.

This recent stretch of futility presents Hoshino’s team with its first valley of the season. Rakuten has lost 10 of 13 and faces series against the Orix Buffaloes, who lead Japan with 88 runs scored, and the first-place Seibu Lions this week.

The next six games will not define Rakuten’s season, but the way they respond to their early stumbles may potentially offer a precursor of what’s to come.

The Eagles began the year with confidence on the heels of an improved performance in 2012 that saw the team finish one game out of a Climax Series spot.

They’re now counting on that experience to help guide them through the rough patches this season.

“I feel like there’s a good atmosphere,” reliever Darrell Rasner said Saturday. “We have a good atmosphere in the clubhouse, in the dugout, everyone seems real positive. There doesn’t seem to be a lot of panic when we don’t do well. Guys seems to be handling the adversity a little better.”

For the Eagles, these lumps have to be a learning experience. The season is a marathon, and getting too high or low at any given time can throw things out of whack. The team has veterans who have to get that message across, guys like shortstop Kazuo Matsui, Jones and McGehee, a trio of former major leaguers who between them have probably seen and experienced it all. It’s their example the younger players will need to follow in order to achieve the heights they aspire to reach.

“I just go out there and lead by repetition,” Jones said. “Kaz is the captain, he’s been here for a long time. A lot of those guys respect him. We get that leadership from him. Us (he and McGehee) as the foreigners, we just have to come here, kind of fit in, and just follow his lead, lead by example, go out and play hard and do the things that we need to do so those guys can learn from that.”

The Eagles have plenty of talent, but in order to win, their mental strength has to match their physical gifts.

They have to work to gain the type of swagger the Yomiuri Giants carry around effortlessly, and how they perform during their current funk will say a lot about whether the Eagles are finally ready to join the ranks of the contenders, or are still flying a little too close to the sun.