That means there will be flashes of brilliance, highs, lows and some growing pains to endure, and the latter cost Seattle in a 2-1 loss to Minnesota in 10 innings on Friday night at Safeco Field.
With the score knotted at 1-1 and Justin Morneau on second base, Matt Tolbert lifted a fly ball that carried near the warning track in left field. Balentien got a late jump on it and drifted back to get near it, but the ball grazed off his glove and dropped, allowing Justin Morneau to scamper home with what proved to be the winning run.
The loss wiped out Seattle starter Felix Hernandez's superb seven innings of one-run, seven-strikeout ball, it wiped out some excellent Mariners defense, including one of the best catches of the year, a three-run-homer saver by Franklin Gutierrez, and it eliminated the team's two-game winning streak, leaving the Mariners at 26-29 for the season.
In the clubhouse after the game, various teammates went to Balentien's locker to console him to little avail.
"I don't feel good right now," Balentien said. "It's a play I have to make. I have no excuses. ... He didn't hit it that far. I just got a bad jump on it. I can't do anything about it. Tomorrow's another day."
Mariners manager Don Wakamatsu agreed, saying the team is still trying to determine the best possible lineup and defensive alignment night in and night out as the rebuilt Seattle roster continues to improve from its 101-loss season of 2008.
"In that situation, right away, as soon as that ball's hit, he took kind of a bad route to it," Wakamatsu said. "He'll come out and he'll work and hopefully that won't happen again.
"I think at some point with a guy like Wladi, you're trying to find out what you have. We have to see what he can do out there. Those are things that obviously he needs to work on, on a play like that in a tight situation. As we go forward, he will make those adjustments."
That's not to say the Mariners didn't play good, and at times, spectacular defense Friday night.
Catcher Rob Johnson made three key plays, tagging Tolbert out at home plate in the eighth, throwing out Denard Span at second in an attempted steal in the ninth, and catching Joe Mauer off third base in the 10th on a pitchout on an attempted suicide squeeze.
And then there was Gutierrez, who scaled the center-field wall on a Jason Kubel blast in the 10th, catching the ball in the heel of his glove and somehow holding on.
"Phenomenal," Wakamatsu said. "He's played as good of a center field as anybody in the league. Just tremendous, gets great jumps. Day in and day out, this guy amazes me and saves a lot of runs for us."
The Mariners struck first in the bottom of the second inning when Mike Sweeney led off with a home run to left field, the veteran designated hitter's third long ball of the year.
But Twins starter Francisco Liriano held Seattle in check for the next four innings. That allowed the Twins to tie it at 1-1 in the top of the third when Carlos Gomez and Alexi Casilla opened the frame with back-to-back infield singles, Span moved them over with a sacrifice bunt, Mauer walked to load the bases and Morneau drove in Gomez with a sacrifice fly to left.
Hernandez's seven sparkling innings lowered the right-hander's season ERA to 3.22. He turned in his team-leading eighth quality start (six or more innings, three or fewer earned runs) and has now struck out at least five batters in 10 starts this season.
"I was hitting my spots today," Hernandez said. "I felt pretty good. It was a great game. Liriano threw a great game. It's tough. But I feel stronger right now. The key is throwing strikes and getting ahead in the count."
Sweeney noticed Hernandez's mastery, too, which is why he said he and the rest of the Mariners' hitters were responsible for the loss.
"He pitched great," said Sweeney, who finished 1-for-4. "It breaks my heart. When he's that good for seven innings, we have to win games. We did a horrible job of swinging the bats, me included.
"We have to find a way to pick it up."
The one Mariner who hasn't had any problems offensively lately suffered a slight letdown, however.
Ichiro Suzuki's franchise-record 27-game hitting streak came to an end on an 0-for-4 night in which he only reached base in the third inning on a walk and ended the game in the 10th by striking out against Twins closer Joe Nathan.
"We wanted him to keep the hit streak going, but we wanted to win the game," Sweeney said.
"Hopefully he'll start another streak tomorrow and we'll start a winning streak."
Doug Miller is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.