Gloucestershire's Jamie Cooke finished 18th in the first modern pentathlon World Cup of the year in Palm Springs, Florida.
His Great Britain team-mate, Joe Evans, 19, took bronze on his World Cup debut.
Cooke, 21, from Andoversford, was part of a three-man GB team competing in the finals.
Fellow Brit Sam Curry finished in 23rd.
Evans, a sports performance student at the University of Bath and a product of Pentathlon GB's World Class Talent Pathway, performed consistently throughout the day at the opening World Cup of the new Olympic cycle.
He crossed the finishing line just eight seconds behind world champion Alexander Lesun of Russia and two seconds off Adam Marosi, Hungary's Olympic bronze medallist.
Evans started the day well, winning 20 of his 35 fencing bouts for joint eighth place with 880 pentathlon points.
Curry won 19 contests for joint 12th with 856 points, while Cooke, Britain's 2011 world junior champion, scored 13 wins for 712 points, putting him 32nd.
Cooke, a former Balcarras School pupil, produced a typically strong 200m freestyle swim to climb up the leaderboard.
His 2:01.00 was the third fastest time of the day and worth 1348 points, pushing him up to equal 27th.
His time was only slightly faster than Evans, whose 2:01.69 was fifth fastest, adding 1340 pentathlon points to his total. That saw him climb up to joint sixth place on the leaderboard.
Curry's 2:07.47 was the 18th fastest time of the day worth 1272 points, putting him 15th going into the ride.
Evans kept up his challenge in the riding arena. On a day when only one rider, Ireland's Eanna Bailey, went clear in the allowed time, Evans dropped just 40 points from the maximum 1200 to add 1160 to his total. That was enough to ensure he went into the combined run/shoot in second place, five seconds behind leader Amro El Geziry of Egypt.
Curry dropped 46 from the maximum to put him sixth overall with Cooke, a former member of Gloucester City Swimming Club, adding 1096 to his total to go into the run/shoot in 25th.
And Evans rounded off a fantastic day with a run/shoot time of 11:35.64 to claim the bronze medal at his first World Cup.
His time was 22nd fastest of the day, earning 2420 points, but it was enough to ensure he finished 10 seconds clear of Russia's world number two Ilia Frolov, who came home fourth.
Cooke climbed up the field to 18th courtesy of a combined event time of 11:23.42 worth 2468. Curry's 12:16.05, worth 2256 points, was 33rd and saw him finish 23rd.
The next World Cup is held in Rio de Janeiro, Brazil, from March 20 to 24. The third event is in Chengdu, China, from April 17 to 21 and World Cup four in Budapest, Hungary, from May 8 to 12.
The World Cup final is in Nizhny-Novgorod, Russia from May 31 to June 2.
