Tim Lincecum gave up seven earned runs in 3 1/3 innings against the Nationals on Tuesday. (Katherine Frey/The Washington Post)

Tim Lincecum was a little less than two hours away from his 17th start of the season, the midway point of his most difficult season as a professional.

He had yet to change into his uniform, instead he wore a pair of soccer shorts, a team hoodie and a knit hat that he wore into Nationals Park a few hours earlier despite the summer heat wave.

There was no sense of desperation, no reflection of his struggles as you watched him prepare.

Instead, the 28-year-old San Francisco Giants right-hander was relaxed as he made his way around the clubhouse, joked with teammates and listened to music on oversize headphones. He even spoke to a Bay Area reporter, taboo for a pitcher on the day he starts.

And when he took the mound on Tuesday night, he still appeared to be the same pitcher that skyrocketed to the top of the sport. His hair was still shoulder length under his Giants cap and his windup contorted in that ever familiar, funky way.

But, the results were quite different. Lincecum’s fastball hovered around 90 mph, roughly four ticks slower than during his 2008 Cy Young campaign. Of the 12 active pitchers who won at least 17 games that season, Lincecum is the only one whose fastball has steeply dropped off. He’s also the youngest.

His velocity dip could be blamed on his 30-pound weight loss after an offseason diet plan. He cut out fast food and weighed just 160 pounds in spring training. He’s since raised his weight to 167 pounds, still 24 pounds less than last season.

He didn’t blame his weight loss for the way he pitched in the 94-degree heat on Tuesday (31 / 3 innings, nine hits, seven earned runs, two walks, two strikeouts). He said it wasn’t anything he hadn’t dealt with before.

“I haven’t treated the heat any different than I did in the last five years,” said the 5-foot-11 Lincecum. “Still doing IVs, still hydrating well, it just got the better of me.”

Along with weight loss, the drastic drop in velocity may be an effect of the righthander’s durability. He hasn’t spent any time on the disabled list over his six-year career. He’s thrown more than 212 innings and made at least 32 starts each of the past four seasons.

He’ll start Sunday at Pittsburgh attempting to enter the all-star break on a high note. He has an 8.45 ERA away from San Francisco’s AT&T Park, nearly double what it is at home. And opposing batters are hitting .297 in his nine road starts.

“You like to keep the mantra ‘it’s not how you start, but how you finish,’ ” Giants Manager Bruce Bochy said. “His stuff is fine, he’s healthy. We’ll need him to pitch like we know he can in the second half.”

He’s allowing a career-worst 9.3 hits per nine innings and is just 18 earned runs shy of his career high.

Lincecum was just 24 years old when he won his first of two consecutive Cy Young Awards. Barry Zito, his Giants teammate, was the same age when he won the award with Oakland in 2002. Zito never turned up radar guns, as he won the Cy Young with an 87-mph fastball and a knee-buckling curve.

But, like Lincecum, he saw a quick dip in velocity. In 2006, Zito’s seventh major league season, his fastball had dropped off my almost three miles per hour. The downed velocity would cause him to transition his pitching style; less than half of his pitches are fastballs now as he gets by with a barrage of change-ups, sliders and curveballs.

“You can’t really skip a lot of work days, the older you get,” said Zito, now 34. “You have to stay on your stuff every day. When you’re a young player, you don’t have to work so hard. You can get to the field an hour before a start, stretch, put on the uni and throw.”

As times goes on, Lincecum will need to adapt, too. He’s no longer the 24-year-old phenom with a blazing fastball. His windup still contorts, but the way he develops his breaking pitches is what will keep batters off balance. Perhaps that’s why he worked heavily on a curveball this spring.

He may still have the same eccentric personality of his younger days, but Lincecum is showing signs of a pitcher in transformation.

“Guys like winning, it’s what we’re here for,” Lincecum said. “I’ll just try to feed off whatever wins we get, whether that’s me pitching that day or whoever. It’s contagious, so I have to get back to that.”