By Chris Lotsbom

Since Sam Chelanga’s first professional race here in Boston last June, things have changed for the diminutive 27-year-old. He now has a sponsorship, an elite training group, and is beginning to establish a professional career, three things the Liberty University graduate was missing when he finished fourth at the inaugural B.A.A. 10K in 2011.

“It’s a good change,” noted Chelanga, who is signed up for all three legs of the inaugural B.A.A. Distance Medley Relay, a series that awards $100,000 to one male and one female athlete who has the lowest cumulative time between three of the B.A.A.’s events: April’s B.A.A. 5K, Sunday’s B.A.A. 10K, and October’s B.A.A. Half-Marathon. Currently, Chelanga is leading the standings thanks to his runner-up finish at the B.A.A.5K.

In April, Chelanga said that he has enjoyed his new surroundings, training under Mark Rowland in Eugene, Ore., as part of the Oregon Track Club Elite.

“When you compare it to college, I’d say it’s a good change, because now you’re more relaxed and focused and you have professional help. And you have the time, you don’t have to go to class!” said Chelanga. “I’m starting to get used to the new training regimin, because I never did gym stuff before.”

Before the B.A.A. 10-K last June, Chelanga expressed his love of Boston, saying that ever since his brother Joshua finished third in the 2001 Boston Marathon, he has envied the city, dreaming of its famed CITGO Sign and John Hancock building. In the eleven years since then, Chelanga’s adoration for the city has only grown.

“The dream is only getting better. And to think, I mean, what if I win the $100,000 here [from the Distance Medley Relay],” said Chelanga with a smile. On Sunday, Chelanga will face 2011 Boston Marathon champion Geoffrey Mutai and 2011 B.A.A. Half Marathon winner Ali Abdosh, among others. Also entered is 2012 Boston Marathon runner-up Levy Matebo, and American Jason Hartmann. Chelanga hopes to come out of the B.A.A. 10K still atop the men’s leaderboard; he is currently winning by three seconds over compatriot Lani Rutto.

The 14-time All-American, though, most looks forward to the day when he can cross the Boston Marathon finish line after running through the eight cities and towns that make up the Boston Marathon course.

“All your dreams, the anticipation. It’s going to be a great day when I do it,” he said, a twinkle clearly visible in his eyes, the excitement building in his voice. “A couple years, maybe one or two. I’m coming.” This year, Chelanga watched from the press truck as his friend Wesley Korir won in 2:12:40.

Chelanga, who is a native of Nairobi, Kenya, has ties to Massachusetts. His wife, Marybeth, is from Plymouth, 35 miles southeast of Boston. The couple, along with Mutai, Moses Mosop, and 2011 Boston Marathon champion Caroline Kilel took a trip to the beach in Plymouth after last year’s B.A.A. 10K.