Chris Estwanik admits defending his Bermuda Marathon Weekend Half-Marathon title will be no easy feat.The former Nike Farm Team runner will lay his title on the line in this Sunday’s 13.1 mile road race in a field that includes past Half-Marathon champion Shadrack Biwot of Kenya.“Shadrack is coming back so I will have plenty of people to chase,” the five-time Bermuda Marathon Derby winner grinned. “Last year I was able to steal victory in the 10K and Half-Marathon but this year it’s going to be a dogfight.“There will be plenty of competition and I will just go out and try and hang with those guys as long as I can. Even if I’m not able to defend my title hopefully I will be able to run faster because of the quality of the athletes that are coming here.”Last year saw Estwanik post his fastest time to date (one hour, eight minutes and 35 seconds) on the Half-Marathon course a day after becoming the only the second local runner behind Cal Bean to win the 10K event (31:03). The former track runner claimed the men’s Half Triangle Challenge title having also won the series’ mile race.Estwanik is using this Sunday’s race as further preparation for April’s Boston Marathon.“I am just doing the half-marathon because I am all-in on this Boston Marathon on April 15 and with that there’s certain training that I’m trying to follow to a tee to ensure an optimum performance at that point in time,” he said.“While I would’ve loved to have done all three (Mile, 10K and half-marathon) it just made sense to really focus on the marathon training which is basically teaching your body to run while you are tired. And the nice thing about the half is that I will be running a significantly faster pace than I would be able to maintain for the full so obviously it will be good training in that respect and will help for the marathon because the international athletes coming over will have superior times.”Estwanik admitted passing up the mile and 10K events wasn’t an easy choice to make.“It was a difficult decision to make because obviously I did it last year and had some success,” he said. “But I will have plenty of competition in the half-marathon so it’s not a bad thing to focus on one event.”Estwanik and his wife Ashley, who is also only competing in the half-marathon, were due to run in last October’s New York Marathon that was cancelled in the wake of superstorm Sandy.“Quite frankly the disappointment of New York not happening is where we are at right now because we invested a lot of time and energy into that marathon,” Estwanik said. “But being the stubborn athletes that we are we kind of reset the bar towards the Boston Marathon and with that comes other sacrifices, so you have to be smart with your training and not just try to push everything like I did last year.”Ashley was the first local finisher and third overall in the women’s field in last year’s half-marathon after crossing the line in one hour, 25 minutes and 53 seconds.Following the Boston Marathon, the Estwaniks will turn their attention towards representing Bermuda in this summer’s Island Games to be held here.“After the marathon we are going to start backing down our mileage,” he said. “We are actually going back to our roots and doing a little bit more of the shorter distance stuff so we can be active participants come July.”