Left-hander Robby Scott entered Friday’s exhibition game against Houston in the fifth inning, with no outs and a runner on first.

An infield single and a walk loaded the bases.

So the streak of impressive outings seemed over for Scott, ever-the-underdog as he tries to make the Boston Red Sox roster.

But after a force at home for the first out, Josh Reddick, the newest Astro, popped to third.

Evan Gattis, who had an .886 OPS against left-handers last year, struck out swinging on a full-count curveball, ending the threat.

Scott, 27, who pitched two seasons with the Portland Sea Dogs, is still impressing. He is your poster child for unheralded pitchers wanting to emerge from the Hadlock Field bullpen and reach Fenway.

“I got that taste of it,” Scott said in January. Scott was called up by Boston for seven games at the end of last season. He allowed no runs, six hits and two walks, and struck out five in six innings.

But no guarantees this season.

“They always talk about it being tough to get there, but it’s harder to stay,” said Scott, who in seven innings this spring has allowed no runs, six hits and five walks to go with five strikeouts.

Scott is competing with Fernando Abad for the second lefty spot in the bullpen (after Robbie Ross). Abad has been pitching for the Dominican Republic in the World Baseball Classic.

The competition is not on a level playing field because Abad has no minor league options left and Scott does. The Red Sox easily can send Scott to Triple-A Pawtucket and summon him when needed.

That could be the case for a lot of Red Sox relievers stashed in the minors. Boston brought in several former, current and future Sea Dogs relievers to major league spring training camp.

There’s Scott, along with Kyle Martin and Luis Ysla, both promoted to the 40-man roster during the offseason. Among the nonroster invitees are Chandler Shepherd, Ben Taylor, Austin Maddox and Jamie Callaghan.

Besides Scott, Martin may be the most advanced, having spent all last season in Pawtucket. Command of his low-90s fastball is key in setting up his killer change-up.

Ysla, a lefty with a mid-90’s fastball, is on the 40-man roster because of his potential. He shouldn’t see the majors soon and even could wind up back in Portland, depending on how the bullpen shuffles shake out.

“From a raw ability standpoint, (Ysla is) really impressive,” said Ben Crockett, the Red Sox director of player development.

Shepherd mixed his pitches well in Portland (1.80 ERA) last year and hit some bumps in Triple-A (3.71). He could surprise this season.

Taylor and Maddox were midyear promotions to Portland last year, and Callaghan spent last season in Salem. They should make for a strong Sea Dogs bullpen, along with Ty Buttery (converted from a starter last year) and Williams Jerez, the Red Sox left-handed project who’s no longer on the 40-man roster.

That’s a whole lot of arms with potential of reaching the majors. Scott, the former independent league unknown, can show the way.

WHILE BULLPEN depth is building for the Red Sox, reliable arms in the rotation are another issue. Boston has five starters, not including David Price, who is likely to start the year on the disabled list. After that the next option appears to be Kyle Kendrick, 32, the former Phillies and Rockies starter signed to a minor league contract.

Three left-handed starters, expected to be reliable backups, are not so reliable – Henry Owens (15.95 ERA in four appearances this spring), Brian Johnson (5.40 in three games) and Roenis Elias (strained rib muscle). The fact Owens and Johnson were among the first players cut from major league camp was telling.

TWO FORMER Sea Dogs were selected in the Rule V draft last December and have a chance of sticking in the majors all this season. Right-hander Justin Haley was drafted by the Padres, then traded to Minnesota. He’s pitched 82/3 innings in six games (10 hits, five earned runs, seven strikeouts, two walks).

Outfielder Aneury Tavarez was drafted by Baltimore and is batting .273/.636 OPS in 33 at-bats. He is 6 of 6 in stolen- base attempts … Another former Sea Dog, infielder Sean Coyle, is on a minor league contract with Baltimore. He has only nine at-bats in major league spring training games, but has been impressive with two doubles and two home runs.

THE WHITE SOX have drawn interest locally after acquiring two of Boston’s best prospects in the Chris Sale deal. Yoan Moncada is batting .265/.918 in 34 Cactus League at-bats. He has 13 strikeouts and no walks. The switch hitter continues to be impressive batting left (.292/1.080, two home runs, a triple and double) and struggles on the right side (.200/.500, one double). … Right-hander Michael Kopech made a relief appearance Friday in a game against the Cubs. In two innings he allowed one hit and struck out five.

Kevin Thomas can be reached at 791-6411 or:

kthomas@pressherald.com

Twitter: @ClearTheBases