"They got a break to tie the game and we got a break to win the game," Oakland manager Bob Geren said.
In the 10th, the switch-hitting Pennington sliced a pitch from right-hander Jordan Walden (0-1) toward left-center. Wells, playing right field this season after winning three Gold Gloves as a center fielder with Toronto, tried a sliding catch and the ball went off his glove as he nearly collided with Bourjos.
"It was just two aggressive guys with speed, and both of them can get to the ball. So something like that is bound to happen," said nine-time Gold Glove winner Torii Hunter, who has been playing right field since Bourjos was promoted from the minors last August. "It's probably the first time that they've ever had a close call like that out there.
"It's difficult to make the call on a ball like that," Hunter said. "With a guy throwing 97 [mph] to a left-handed hitter, he's going to be a little late on his swing. And if you're in center field, you've got to know that the ball is going to tail back to left with a little sink to it. Peter's so fast, he got there early. I mean, speed is good, but sometimes you get to balls that nobody expects you to get to. You've just got to give them a little more time playing with each other."
Daric Barton was intentionally walked with one out, and Jackson delivered the run with a high chopper to shortstop.
Oakland's Tyson Ross scattered four hits over seven innings and induced three double-play grounders in his second start for the injured Dallas Braden. The right-hander, who turned 24 years old last Friday, walked one and did not allow a runner past second base in his fourth major league start before handing a 1-0 lead to the bullpen.
"I was pretty happy with my results," Ross said after his 76-pitch effort. "I made an adjustment from my last start and just tried to simplify my motion. I attacked the zone early, got my sinker over the plate and got a lot of ground balls. The only thing that matters is that we got the W, and it's going to be a nice plane ride home."
Grant Balfour pitched a perfect eighth and Fuentes (1-2) took over in the ninth. Pinch hitter Maicer Izturis reached on Kouzmanoff's fielding error, Mark Trumbo went in to run for him and Bobby Abreu doubled home the tying run on a 3-2 fastball.
"He's a good hitter in any situation," Fuentes said.
The blown save was Fuentes' second in eight attempts. The 35-year-old lefty is handling the closing chores in place of Andrew Bailey, who has yet to pitch this season because of a forearm strain that occurred during an exhibition game on March 14.
Fuentes, a four-time All-Star who posted four seasons with 30 or more saves after becoming a full-time closer with Colorado in mid-May 2005, led the majors with a career-best 48 in 2009 for the Angels -- who traded him to Minnesota last August.
Brad Ziegler retired the side in order in the 10th for his first save of the season.
Dan Haren got a no-decision despite giving up an unearned run and three hits over seven innings with five strikeouts and two walks. The three-time All-Star, who won 44 games during his three seasons with the Athletics, remained 2-0 with a 2.67 ERA in five career starts against Oakland. He lowered his season ERA to 1.23, second in the AL behind teammate Jered Weaver's 0.99 mark.
Oakland scored its first run in the third inning without the benefit of a hit. Landon Powell walked on a full count, Kouzmanoff reached on a fielding error by first baseman Howie Kendrick, David DeJesus got hit on the foot with an 0-2 pitch and Barton hit a sacrifice fly.
"I was all over the place in the beginning and falling behind in too many counts, trying to be careful," Haren said. "I didn't do us any favors with a couple of leadoff walks, and then I hit a guy 0-2 after the error and pitch out of that. So I was bending but not breaking. The last couple of innings was as good as I've felt all year."
After the game, the Angels optioned RHP Matt Palmer to Triple-A Salt Lake in anticipation of activating LHP Scott Downs from the 15-day DL on Friday. ... Weaver will make his next start on Sunday with an extra day's rest. He finished April 5-0 with a 1.48 ERA, after beating Kansas City on March 31 with 6 1/3 scoreless innings for the first of his six straight wins. ... DeJesus extended his errorless streak to 262 games, the longest among active outfielders. Hunter had an errorless streak of 265 games that ended on Sept. 18, 2009, when he was still playing center field. He has committed only three errors since that one.