Jonathan Roof stood on second base, representing the possible winning run for the Portland Sea Dogs in the bottom of the 10th inning Sunday afternoon.

Who might drive him in?

Mookie Betts, Travis Shaw and Shannon Wilkerson have been promoted, and the Sea Dogs hadn’t yet reached the heart of the order – Devin Marrero, Blake Swihart and Sean Coyle.

But when Derrik Gibson stepped into the batter’s box, the Sea Dogs could not have been in better hands.

Gibson, a one-time prospect who is having his best professional season, worked a 2-1 count and got the fastball he was expecting. He singled into left field to score Roof and give Portland a 5-4 victory over the Bowie Baysox before 7,236 at Hadlock Field.

A second-round draft pick in 2008, Gibson, 23, is beginning to fill the expectations placed on him from the start. After going 2 for 4, Gibson is batting .296.

“Offensively, I think things are starting to make sense to him,” Sea Dogs Manager Billy McMillon said. “His hands are working well and he’s able to get more hits.

“It’s good to see. He’s got some talent.”

With Portland down 4-2, Gibson helped tie the game in the eighth inning, doubling home a run and then scoring on Marrero’s single.

Entering this season, Gibson was batting .243 as a pro.

“I just stick with it,” said Gibson, who is in his third season in Portland. “Improving in little increments. Not trying to think too far ahead and not too far behind.

“The Red Sox believe in me and I believe in myself. I’m just happy to play this game every day.”

Defensively, Gibson has moved from the infield to the outfield. Since Betts and Wilkerson have been promoted and with Henry Ramos and Peter Hissey on the disabled list, Gibson is the center fielder.

“I couldn’t be more pleased with his center-field play,” said McMillon, who has often spent extra time before batting practice working with Gibson.

“But he’s not a center fielder. He’s an infielder. We got to find ways to get him back in there.”

Just as long as Gibson is in the lineup, he can make a difference, like he did against Bowie reliever Fabio Castillo.

“He threw three breaking balls in a row and I thought he would come in hard,” Gibson said. “(I was just) trying to be ready for the fastball.”

Gibson bounced a single into left, and Roof raced around third and scored.

Roof, recently promoted from Class A Salem, also scored in the fifth. He doubled and came home on Heiker Meneses’ double.

Portland’s other run came on Coyle’s solo home run – his fourth – in the second inning.

Portland starter Mike Augliera, pitching on his 24th birthday, gave up four runs on nine hits over 62/3 innings.

Miguel Celestino (1-2) picked up the win with two perfect innings of relief.

NOTES: The Sea Dogs (41-22) lead the Eastern League’s East Division, while the Baysox (32-30) are third in the West. … Portland takes today off and begins a three-city road trip Tuesday in Altoona, Pennsylvania. The Sea Dogs return to Hadlock Field on June 20. … Brian Johnson, who had his turn in the rotation skipped last week, will start Tuesday. The Red Sox routinely have their pitchers skip a start a couple months into the season. Henry Owens’ turn is being skipped in Altoona. … Former Sea Dogs starter Chris Hernandez carried a no-hitter into the seventh inning for Pawtucket. He allowed one single and lowered his ERA to 3.16.