SAN BERNARDINO — It was a rough first game for Pomona resident Jessie Mier.

Mier, a catcher just activated before the game, committed a throwing error to allow two runs to score in the top of the 10th inning as the 66ers fell to the Modesto Nuts 5-4 in the finale of a four-game series before 4,077 at Arrowhead Credit Union Park on Saturday night.

Mier had been the Sixers’ bullpen catcher all season long and never activated, until Saturday, when Kenley Jansen was sent to Triple-A Albuquerque in what is believed to be a temporary assignment.

Mier was activated and started, and Modesto was 7-for-7 stealing bases off of him, although several of them weren’t his fault. Modesto’s one caught stealing didn’t involve Mier as starting pitcher Josh Wall threw out Charlie Blackmon trying to steal in the third.

Mier also had a passed ball and the critical throwing error.

With the score tied 3-3 and one out in the 10th, Matt Repec singled and Mike MItchell walked for Modesto against Marlon Arias (1-1).

Then as Radames Nazario struck out, Repec and Mitchell executed a double steal of third and second, respectively. Mier’s throw to second was more unlucky than it was bad, but it ricocheted off of Mitchell and into left field, allowing both runners to score for a 5-3 Modesto lead.

The fact two runs were scored was especially costly to the Sixers, who came back with one run in the bottom of the 10th against closer Craig Baker, who entered the game having allowed only one run in his previous nine appearances and was a perfect 15-for-15 in saves.

Baker made it 16-for-16 despite Christian Lara scoring on Justin Fuller’s fielder’s choice grounder. Fuller got to second on a wild pitch, but Trayvon Robinson grounded out to second to end the game.

It was a disappointing end to a game that had several positive signs.

Josh Wall, in his first unrestricted start recovering from a groin injury, pitched six innings, allowing one run on four hits while striking out four and hitting two batters. He left with a 3-1 lead but relievers Miguel Sanfler and Jacobo Meque allowed five straight batters to reach base in the seventh with two outs as Modesto scored the tying runs.

Robinson had two hits, including his sixth home run, and made two diving catches in left-center to steal hits away from the Nuts. Scott Van Slyke also hit his sixth homer of the season for the Sixers.