David Ortiz delivered a two-run single to center on the first pitch he saw in his return from the DL. (AP)

“Enjoy the show tonight.”

The words seemed like an idle boast a few hours before Friday night’s Red Sox-Royals tilt. After all, when David Ortiz uttered that sentence, it had been almost six weeks since he had stepped into a batter’s box against live pitching in a game. The slugger had been out since July 16, when he injured his right Achilles tendon — an injury that was initially expected to sideline him for only a matter of days but that persisted well beyond that.

In that situation, rust would be natural, even expected. Thus it was that he left his teammates astonished when he stepped to the plate in the bottom of the first inning, saw an 87 mph sinker from Royals left-hander Bruce Chen and, with runners on second and third, immediately lined it up the middle for a two-run single to center.

“We must have pretty good [batting practice] pitchers to simulate Bruce Chen’s slider and fastball,” joked manager Bobby Valentine. “It’s very impressive. David is world class. World-class players can do special things.”

Ortiz would add a double to the gap in right-center in his second at-bat before striking out in his final two plate appearances. His 2-for-4 night — in which he drove in half of the Red Sox’ runs — underscored his impact on his team’s offense and team. At the time of his injury, the Sox were surging at the start of the second half. The team had improved to 46-44 in a tightly bunched race for the two wild card spots, thanks in no small part to an offense that was averaging exactly 5.0 runs per game.

But without Ortiz — who was leading the AL in on-base percentage, slugging and OPS at the time of his injury — the offense and the Sox’ season took a drastic hit. The Sox went 13-22 while averaging 4.6 runs per game, a stretch during which the team was wildly inconsistent.

The return of Ortiz, even on a night when Adrian Gonzalez was a late scratch from the lineup while rumors of a potential trade swirled around him, seemed to put a charge into the Red Sox for obvious reasons. He remains an elite hitter, with a .318 average, .415 OBP, .611 slugging mark, 1.026 OPS and 23 homers — all marks that, despite the lengthy midseason absence, top the club. His ability to roll back into the batter’s box after a lengthy hiatus and produce without benefit of a rehab assignment underscored his considerable talent.

Still, it would appear to remain an open question what Ortiz’s availability will be going forward. The 36-year-old visibly hobbled while running the bases, most notably when he pulled into second base (without sliding, despite a relatively close play) following his double. Ortiz acknowledged that he continues to feel discomfort in his Achilles, and that he’ll have to monitor the injury over the next couple of days. As satisfied as he was to offer offensive production, he sounded a note of uncertainty about the permanence of his return to the lineup.

“I’m still having issues with my foot. After I hit that double on the second at-bat, the next thing I think about is how my heel is going to react. It got into my head a little bit. It’s getting sore, so we’ll see how it goes the next couple of days,” Ortiz said. “I want to give it a try and see how it feels, especially seeing the team and how things were going and having issues with the offense. Like I said, we’ll see how it goes the next couple of days.”

Of course, with the Red Sox mired six games below .500, the immediate future is only part of the equation for the free agent-eligible slugger. The potential deal of Gonzalez would underscore the need in the Sox’ lineup for a legitimate middle-of-the-order force. With Gonzalez in the lineup, the absence of Ortiz was dramatic. If Gonzalez is gone and Ortiz left, the Sox might find it nearly impossible to replace his production.

At the same time, the potential blockbuster would liberate considerable money for the Sox to try to re-sign Ortiz (who is earning $14.575 million this year on a one-year contract). While it seemed fair to wonder whether a decision by the Sox to sell off several key players might diminish Ortiz’s desire to return, the slugger suggested that his desire to remain in Boston would not diminish.

“Of course,” he said of whether he wanted to remain in Boston after this year. “Why not?”

For now, the Sox are simply grateful to have their familiar force back in the middle of the lineup, and to be amazed by what he is capable of doing.

“I was over there when he told you guys to sit back and watch the show. That was awesome,” enthused teammate Andrew Bailey after the game. “First pitch, sure enough, two runs. He’s awesome. You can’t say enough about that guy.”