Photo: Alex Trautwig, MLB Photos Via Getty Images

SCOTTSDALE, Ariz. — Closer Mark Melancon reached a milestone Wednesday, pitching in a game for the first time since a September operation to release pressure on the pronator muscle in his right forearm. The results were good. He faced the Padres’ Manuel Margot, Raffy Lopez and Wil Myers, and retired them all.

Melancon is aiming to be ready to close on Opening Day in three weeks, despite a slow approach this spring.

“That’s how we’re going about it,” he said.

And yet, Melancon struggled to find the right words several times when asked how his arm felt. The best answer for the Giants would have been, “Never felt better. Raring to go.”

Melancon did not say that. In fact, he deliberated for a good spell before he said, “It’s progressing. I don’t think we expected it to be perfect from Day 1. Part of having surgery is going through that.”

Reporters tried to parse the statement. Was Melancon going through normal discomfort, or did he feel something in the affected area?

“It’s hard to tell the difference sometimes,” he said. “Discomfort is part of the process. I don’t view it as a negative thing. That’s part of it.”

The Giants need a healthy Melancon for the back end of the bullpen, even with the additions of Sam Dyson last season and Tony Watson this spring.

Melancon tends to be guarded when discussing his arm. The truer test is not what he says, but how often he takes the ball. A reliever ordinarily pitches every other day here. Melancon was unsure if he would pitch again Friday, saying he needed to discuss that with the staff.

Manager Bruce Bochy said he expects Melancon to be ready by Opening Day and should be able to pitch back-to-back days by the end of spring, the last box a reliever checks off. Bochy sounded confident that Melancon will be ready and, just as significant, that the 32-year-old is healthy.

“He’s thrown live BP,” Bochy said. “It’s not like he’s been hurt this spring.”

Briefly: Bochy said that Buster Posey, who has played just one game, had two at-bats and caught two innings in the Cactus League, is expected to start Friday. He originally was to play Wednesday, but the staff wanted him to test his left ankle in drills before having him play. … Bochy played would could be his regular lineup against right-handed pitchers, minus Posey. Joe Panik and Brandon Belt hit 1-2, which they might do during the season, followed by Andrew McCutchen, Evan Longoria, Brandon Crawford and Hunter Pence. Bochy was coy about where Posey would be inserted. Bochy smiled and said, “seventh or eighth.”

Henry Schulman is a San Francisco Chronicle staff writer.

Giants 4, Padres 4 (10 innings)

Notable: Madison Bumgarner allowed two runs over 31/3 innings in his third game. He struck out six and has 15 strikeouts in eight innings this spring. … Chris Stratton allowed two runs, one on a ninth-inning homer by Dusty Coleman that tied the game. … The Giants jumped on San Diego starter Tyson Ross for two first-inning runs, on a Brandon Belt single, Andrew McCutchen walk, Evan Longoria double and Brandon Crawford single.

Quotable: “I noticed it. It definitely catches your attention. I didn’t come in and look at the lineup and see who’s playing and who’s not. You just walk onto the field and see those names. That’s pretty good feeling.”

— Bumgarner, on seeing the entire Opening Day lineup, minus Buster Posey , on the field Wednesday.

Thursday’s game: Giants at Mariners, 5:30 p.m. TV: MLB Network

— Henry Schulman